Back in the days before Internet, I used JD Whisker by mail-order. I'd phone, then post a cheque to them. Happy days!
Nowaday's I've used Mercian Cycles. Although they're on the 'net http://www.merciancycles.co.uk/
they don't (as yet) have on-line ordering, but if you give them a call and ask about stuff, if they have it in stock, they'll post it off straightaway. They should be able to get hold of any Campag spares.
Give them a ring, and ask what they've got.