Service pattern rifle

Hi I have a service pattern Webley Air Rifle which requires some work but is mostly complete, it is missing the parts that make up the flip up aperture sight, the frame is there but that is all. I would like to make a replacement but need drawings and sizes, in fact anything to give me the dimensions, etc.
Hope someone can help. Fredocrete

you do know theres a company in birmingham that supplys any part for your service rifle