OK so bolting from the inside is an option, although on the Sheldon Brown website they seem a bit wary of that option. I'll bear it in mind though, thanks billso
Bedraggled: Those SJS ones are too long, thanks though.
No JD is not online They are atalogue only and maybe trade only too. As I am trade I can order from them.
Those 105 calipers I mentioned are BR-1050 and are £22 for the pair 39-49mm drop, single pivot design in silver. They have Q/R cam as well.
They still list them I bouht a set for my Alan earlier this year. Quite how they have old stok like this I don't know but it useful for retro builds.
Ok these would be period correct, I might give them a call and see if they will supply me. Question though: are the modern dual pivot better performing than single pivot like these?