Apologies to the OP if this post takes the thread astray, but I am in a similar situation. Currently have Spendor SP3/5r2 in a small room, running them with a modded Gan1. I will be setting up a slightly larger room tthis summer and want to stay with the British sound. Thinking perhaps of Harbeth 30.something or C7es3. At Axpona one room was using some Spendor Classics (I don't remember which). That was a sweet sound. Unfortunately the Spendor Classics are quite pricey in comparison to the Harbeths.
By the way, the OP may want to give a listen to some of the Gan amps with these speakers. In my limited experience (Gan1 and Spendor SP3/5r2) I would describe the sound as effortless, non-fatiguing detail. Insightful, perhaps understated, but very pleasing. It draws one in such that I am reluctant to end a listening session. I haven't tested this, but I suspect that the nature of the Gan amps is to enhance the sound signature of such speakers. Just my 2 cents. Best of luck.