this is what i needed, in the end i cut the rough shape on to a peice of cardboard and then cut away at it and then remarked it and cut more away................ you get the idea. i then used that as a template to cut the ply. i was not 100% bothered about the ply being spot on, just near enough was what i was after. after this was all fixed up i covered it in cladding, because the cladding is only about 100mm wide it is easier to make your way across the front marking and cutting each one as you go for a better finish.
funny enough, i just finished mine today, will post some pictures up over the weekend.
i am no carpenter but i am happy with how it turned out.