Gav how much to weld a head?
I would speak to Les Collins racing, I can't say how much exactly because I've never actually had it all done.
My E31 cylinder head repairs (required some welding) along with new valve seats, reground camshaft, water blasting etc.. cost me around $2k all up. But E31's are getting so hard to find now that it was worth saving in my opinion. These E88's make sense if you can get them at the right price.
I believe they might not quite have the same short side radius as a P90 though? But I tend to view them as the high compression version of a P90. But the real value / desire is for SC racing folks.