A question or two on a Webley Premier air pistol

[slow_runner]

Hi, it has been a while since I last posted.
I have a Webley Premier with battered grips and a missing stirrup latch. I think that the original latch is sintered and prone to breakage?
It has been laying in a drawer for a while and recently a latch was offered so I have been thinking that it is time to get this Premier operational again.
What other Webleys have interchangeable parts? More especially, are the early Webley Senior stirrup latches and grips a suitable replacement.
Is this a straightforward swap over of parts if I can find them, is there any fettling involved? - I may have a lead on the stirrup latch from a Birmingham 4 Senior model Senior and would this be suitable? It is a distance away so a simple trial fit is not possible.
Cheers, I would appreciate your direction. Thanks for your advice