Apologies for the delay Patricia.
Yes - even the most stable roses vary with soil and season and all the more reason to record descriptions in different seasons and locations to build up a broader picture of their range of variation.
In answer to your question about how it compares with 'Catherine Mermet', if comparing with the 'Catherine Mermet' in commerce all over the rose world today, the bloom form is different but the most conspicuous differences are in the leaves and sepals. The leaves of 'Catherine Mermet' tend to be quite coarsely serrated along the entire margins and to have undulating, buckled edges and the leaves themselves are quite widely separated, lending a sparse look to the plant. The leaves of "Blackwood Inn West" are more attractive - reasonably flat and even in comparison, with serrations that become coarser towards the tips of the leaflets and the leaves are closer together, giving the plant a well-clothed appearance.
The sepals of "Blackwood Inn West" reflex fully in the open bloom, while those of 'Catherine Mermet' often only partially reflex, leaving what we have come to recognise as that characteristic 'starfish' of outward pointing sepals that is most conspicuous after the petals have fallen.

The most detailed early description we have of 'Catherine Mermet' accompanies Plate CCCLXXXI in The Garden, March 24, 1883 (pp268-9)

"CATHERINE MERMET TEA ROSE
This is at once one of the most chaste, beautiful, and useful of all the Teas. At first blush it somewhat suggests a likeness to La France, so recently illustrated and described in THE GARDEN. It has, however, a deeper tinge of flesh colour in its rich and delicate petals than that variety, and there is a dash of green in the shading of its petals in the place of the pale lilac, almost running into French white, that adds so much to the softness and refinement of la France. Both Roses are globular in form, as may be seen from the illustrations, but Catherine Mermet is less pointed in the centre, hardly so high, more round and open, with the petals more imbricated than La France. Catherine Mermet is light rose or delicate flesh-coloured, large, perfect in form, globular, with centre open (I do not mean by that showing the eye, but full and imbricated). It is a free rather than vigorous grower, though several authorities call it vigorous, the wood and leaves in a young state being highly coloured – nearly purple, the spines strong, hooking downwards, large, and very sharp. It blooms freely, and the bloom is one of the most beautiful in all stages, from the opening bud of deep rose colour, just peeping forth from its large, enfolding, green calyx, to the last. Having plenty of material and good form, this is one of the Roses not by any means too numerous of good staying properties, this proving as useful and reliable for exhibition as for general purposes. The fullness of Roses as a means of adding to the durability of single blooms is one of those qualities that has not yet received the measure of attention it deserves. The Roses, as a matter of course, soon expand all their petals, and so reveal their poverty by opening wide their eyes; whereas full Roses of the type of La France and Catherine Mermet have such a prodigal profusion of petals, that they seldom or ever unfold more than a moiety of them. This is a point well worth the attention of our hybridists and raisers of New Teas and other Roses.... M.J.B. Guillot, the younger, the raiser of La France, as also the high honour of raising this Rose; the former was raised in 1867, and Catherine Mermet in 1869. Had there been a longer interval between them, one might have supposed they might have been partly cause and effect. But that is impossible, and it is more probable that both were prizes from some happy and successful endeavour to unite some of our older Teas or Chinas with our best perpetual or other roses... This Rose, like La France, has a great future before it. Such cruel weather as we have just had, and terrible slaughter as I now find the last fortnight’s winds and frosts have inflicted on Tea and other roses in the open, will but render such valuable sorts as Catherine Mermet more valuable than ever under glass. If my memory and note-book serve me aright, this was one of the best varieties among that charming collection of Tea Roses in pots, exhibited by Mr George Paul at the great show at Manchester last year, that created so much interest and had such a stimulating effect in inducing many to grow Tea Roses in 8-inch or 10-inch pots. The splendid examples, several yards high and through, exhibited by Messrs. Veitch, Turner, and others, were simply magnificent. But their very grandeur discouraged general imitation while most useful in revealing the full power and capacity of the Rose as a pot plant. But when the public saw a large collection of most of the best Tea Roses, such as Catherine Mermet, in flower in 8-inch or 10-inch pots, in robust health and with foliage to the rim, with a capital head of buds and flowers for the third time within the year, the sight brought Rose growing in pots within reach of many possessors of a pit or frame. The tiniest greenhouse or window garden should have all these positions, and for forming beds and masses in the garden, on the lawn, and in sheltered, warm nooks and corners in woods, I prophecy a great future for this delicately soft and rich Rose, Catherine Mermet. .... D.T. FISH

Mr Fish explains describes the bloom of 'Catherine' Mernet' as: "perfect in form, globular, with centre open (I do not mean by that showing the eye, but full and imbricated)." while "Blackwood Inn West" tends to reveal its eye of bright yellow stamens as it opens.
The prickles of 'Catherine Mermet are described as "strong, hooking downwards, large, and very sharp." Those of "Blackwood Inn West" are certainly sharp, but are straight rather than hooked and range from out-ward pointing to descending.
I've not been growing "Blackwood Inn West" long enough to say with confidence that its bloom never has a green tinge but looking at photos, I cannot see any evidence of the "dash of green in the shading of its petals" noted by Mr Fish in 'Catherine Mermet'.

I'll check the roses you have listed on the front page as possible contenders for "Blackwood Inn West" and ask Hillary if she can do the same.
Unfortunately there is an absence of useful & detailed descriptive material for so many roses, and in the end you can only muse and speculate and often the best you can do is to eliminate some of the contenders.
Will also add more photos taken at the HRIA repository at Renmark.