Hey Adrian,
It took me a long time to trace the history of those latches from the original WWII manufacturer through all the later companies that either bought the earlier businesses as they went bankrupt or ultimately purchased the manufacturing rights to them. The people with the current rights (as of March 2007) to the items are Shepherd Caster Corporation in Michigan. Their web address is
www.shepherdcasters.com but they only sell parts to other companies which are their qualified distributers. I’d recommend you contact them through their web site eMail links and tell them the parts you are looking for and they should be able to recommend a distributer in the UK or Europe for you.
For the parts, the fastener is number 505564 and the strike is number 505555. To keep things confusing, some of their internal catalogs show the fastener as ZLA1002x and the strike as ZL1023X-B. The actual description when I got a sample from the manufacturer direct showed the fastener as Bassick Parts ZLA1002PS/LW17 and the strike as Bassick Parts ZL1023PS/LS29. Prices will vary with quantity but for reference, the fasteners are less than $5 each and the strikes are less than $1 each.