Graham, I think that you asked a perfectly fair question and deserve (in fact, the UK taxpayer deserves) a properly considered answer. Here's my attempt at part of one.
Firstly, there is absolutely no reason why the UK should repeat another Customer's airworthiness and capability assessments if those provide the necessary evidence to comply with UK regulatory requirements - and in many cases, they certainly should do so.
Too often, though, the independent evidence is not available - and there are a number of reasons why that might be. Those reasons range from commercial or security considerations, through unwillingness of the foreign Customer to release the information (e.g. for resource reasons), to the foreign Customer's evaluation actually not being very good. (Say it ain't so.) There's also the situation where the aircraft/system/whatever is being procured to operate in a different role to the original Customer. Perhaps rare, but it happens.
If evidence
is available, then great - use it, and the UK T&E community may "simply" act as MOD's advisors to confirm nothing has been missed out. (Why can't MOD do this themselves? Well, as several threads on the Military Aircrew forum have identified DE&S have deliberately divested themselves of this over the years.)
If it is NOT available, then what?
MOD cannot ignore their regulatory requirements and remain within the law - and post Haddon-Cave, is it likely anyone would dare? (Cue tucumseh!)
So, compliance with Def Stans, JSPs and the AOF needs be demonstrated - and without our own UK T&E capability, how would MOD do that?
A complete answer to your question has a number of other parts, including "Why do we need an independent T&E organisation, when the manufacturer has done his own testing?" and "Why do we have separate organastions to do Operational T&E and Safety T&E?" I may come back later to consider those, although the answer to the second can be summarised as "For no sensible reason, really".
PS Vertico at 11:57 yesterday - great post. However, you have maintained the fiction that only TPs do T&E. Who are all those non-aircrew people hanging around and far outnumbering them, then?
