Ply is the best bet for a repair, if the rest is shot you could replace the lot, as long as its a good quality ply it should last, plus you can give it a coat of paint so its not so obvious.
If the rest is looking in need of repair, it could well be worth replacing the lot with upvc, soffit, facia and gutter, ive done mine myself on a semi detached, and its not as difficult as you would think, but i did have the house scaffolded to do other work, making the access easy.
You could try the local paper, theres always ads for carrying out this type of work, and they bring their own access equipment as well.
