Ok so I took the door panel off again today to have a better look at the front speakers and also managed to take some better photos so you can see just whats there.
You can see the distance from the window glass to the speaker bracket is just over 2" (55mm). I have fitted a speaker adapter which I picked on from Ebay for £7.99 and this then gives just over 3" (80mm) clearance. The other photos just show the speaker in various angles.
Hope this gives you some ideas.