I've only made claim on a part deposit once.
The T rolled and I received no problem, this was a couple of months after the T had departed and were pestering me for their deposit. I just said that I don't have it, true, and that it's with the DPS. It was then that I raised the claim with the DPS.
I view that as the T's are given all the required paperwork and references at the start of tenancy (well within 14 days) and I include the references on all statements. As it's their money they wish returned it's their problem.
I think we have done enough administrating of the deposit at the start and if they can't organise their paperwork and inform the DPS of updated contact info tough.