As far as I am aware Halkey Roberts no longer have a distributor in the UK for their valves. They used to be distributed by Beaumont Medical, but they gave up a few years ago.
Suggest you contact them direct.
Contact details as follows:
Halkey Roberts
11600 Ninth North Street
St Petersburg
Florida 33716-2119
Tel 001 727 577 1300
Fax 001 727 576 8337
www.halkey-roberts.com