"mo" wrote in message
...
....
I have heard of hammer in fixings, but can i get one this big and are they
as strong as traditional wall plug method?...

Look for frame fixings, which are designed to fix door and window frames
e.g.

http://www.screwfix.com/prods/15978/...5mm-Pack-of-10

You will probably need to counterbore, as they are not really designed for
100mm timber. AIUI the masonry hole should be the length of the threaded
part. IME they are superior to screws in wall plugs.

Colin Bignell