I've been doing some extensive research on this. As I have an old Peugeot 501 frame for the build I'm currently doing and I'm struggling to find some 1" rigid forks to fit the 1" head tube. I've been looking possibilities of reaming out the HT to fit a 1 1/8" headset and/or machining down a 1 1/8" head set to fit a 1" head tube.
Since then I've found 2 guys in the US who make they're own 1" head sets to fit a 1 1/8" fork steerer. I think there's a lot of older American frames/cruisers and bmx's that have 1" head tubes. But this is ideal because it means you can run newer gear on an older frame.
So my question is, instead of me forking out $45-$50 dollars + delivery + whatever import taxes I might have to pay... does anyone in the UK make these? Maybe a frame builder?