Have you tried giving Bloctube a call the 2nd generation of the firm still exists
Purley marine now by the look of it.
BLOCTUBE MARINE
SERVICES LTD
Unit 5, Felnex Close,
Cross Green,
Leeds, LS9 0SR
U.K.
Tel: +44 (0)113 248 4827
Fax: +44 (0)113 240 3351
email:
bloctube@aol.com
Asked a couple of the old fossiles here and they remember them out Oxford"ish" way.