Hi Waka
I think the type of lock you are referring to is called a rim latch or rim lock. Not many made in the UK these days. I think a lot of them are cheap bent steel/brass jobbies from the Far East, such as those sold by
Locks OnLine or
World of Brass although any competent ironmonger should be able to supply them. You can still get good quality ones from one or two companies like
Holloways of Ludlow,
Blackstage and
Cast In Style but to match your lock a trawl through the architectural salvage merchants may be in order. If it is broken I have a contact who repairs thise type of lock and may be able to assist.
Philly, best source of reasonable quality British-made box, till and desk locks I know of is
A E Squire in Willenhall - don't know if they sell direct in small quantities, but the link may be useful for competition entrants.
Scrit