What an amazing response, thank you so much!
And so many things I've never heard of, sending me to google.. I wonder does Frank P's suggestion win prize of most opulent? Although an Alpa also looks a wonderfully exotic beast.
I can confirm for posterity that when OurManinTangiers sold me his M6 it was pristine... Like one of those ones people buy to put on a shelf or in a safe. No sense in which it already looked like it had been to hell and back.
The honest truth is I'm not quite sure of what the budget might be and must find out with delicacy. Not a situation I've ever been in before.
But I am enjoying the desert island quality of these responses!
MF is interesting. I have had access to a Hasselblad for a little while, as one was used in a production of a play of mine and then hung around. Such a gorgeous machine but I didn't find myself using it often, perhaps because of a lack of familiarity or having no skill in focusing it. But I'll read about these other suggestions, never held a Rollei etc.. Not sure how much I'll use it.
Really my major use has been black and white with the M6 and a couple of lenses, an m9 in the same manner (and trying to learn to use colour better) and the wonderful 105mm lens with the nikon.
Thank you so much for your kind replies, if I end up getting nothing I've learnt of a good few things...