Amazing, thanks guys, much appreciated and very reassuring!
I'll get that all sorted and come back here.
Re speakers, I had a look at speakers on eBay and its going to be tricky to find something that isn't rubbish, too old and/or damaged, stupidly expensive or wrong spec/size.
If impedance isn't critical, my option would probably be something like wharfedale super range, that's around 10 ohms speaker, full range and still very good.
Old lower impedance speakers would be blown by modern types but then again, the latter would be half the size so might look a bit odd in such a big cabinet and yet again I'll have to recreate the speaker board as currently have original 12 inch one and new 10 inch speaker board.