So I took the Spendors and AE1 Actives back to Audio Gold - the Spendors reluctantly... they are beautiful things but they didn't solve my problem. Once it's sorted with the Proacs I'll see what pennies I have left and hope no one has bought them. However I didn't return home empty handed - a loaner Quad 606 has been wired up in place of the Nord most of the afternoon.
First switch on was a bit of a disappointment. Still the same sharp trumpets and painful pianos. Slightly dispairing I cast around and my eye fell on the big, bare, white concrete wall about 8 inches behind my head. I pulled up the two big, flat sofa cushions either side of me and propped them to my rear, against the wall. Back on went Miles Davis... and... bliss. I owe an apology to EllisDJ (and probably a few others) who suggested I should look further into room treatment from the outset - you were dead right.
Since then I have been switching back and forward between the Quad and the Nord. The Nord wins on separation, timing and bass control, but the Quad takes it for organic musical involvement, emotion and fun, and for me that's a much bigger win. It will be interesting to hear the Sparkos and Croft power in comparison when they arrive, but for the time being the Quad is staying connected.
Now to find some domestically-acceptable room treatment - any suggestions?