I don't know about the UK, but when I was in Fremantle, Western Australia, a couple of years ago, I bought some parts from a Chandler there. At the time, he had an assorted stock of Barlow spares, and said that if I ever needed any spare parts, to fax him with the details of the winch and part required. With the use of a credit card for payment, he would send the parts (if he had them) to the UK.
Don't be put off by the name, as the chandlery shop had a good selection of new boaty bits, as well as some "used-but-good" stuff.
The person to contact is Trevor Richards of Yacht Grot, 57 Queen Victoria Street, Fremantle 6160, Western Australia.
Phone 61 8 9430 6766
fax 61 8 9335 1276
The winch details he requires are on the bottom (underside of base).
At last years Southampton Bpat Show I picked up a leaflet from Sothern Cross Marine. Phone 01425 482777 Fax 01425 482557. They claimed to have or could make spares for all Barlow winches.
Good luck
Dan
I have used Arco-Winches to source spares for a Barient winch - they deal with Barient and Barlow. I had a short wait until a batch of the appropriate part was manufactured, but the bits arrived and fitted perfectly. I believe they may have bought up the manufacturing rights and tooling. I had problems contacting them though, letter and e-mail went unanswered. A phone call did the trick , and they couldn't have been more helpful.