Found this frame on Gumtree to replace the recently departed B-BSO. Chap will take £35 for it.
Going to cannibalise the B-BSO to create new C-BSO, although may treat m'self to a new bottom bracket as mine is gubbed.
This is v. budget cycling as you may realise (the baby budget is bigger than the bikie budget :)) but hopefully it won't need to last too long, just looking for something solid to sit on.