Cheers kev for your reply,the fibre glass repair is only to tidy up car for MOT which is due.I`m trying to get replacement panels but this taking longer than i expected and MOT will run out before i get them.
if the hole is not within 30cm of a seatbelt , steering or suspension mounting then you can fill it up any way you choose , welding would be a better repair than fibreglass as the rust will continue to munch away unseen behind fibreglass.
GOT RUSTY HOLE IN LOWER REAR CORNER/REAR WHEELARCH,BOOT FLOOR IS OKAY.WHEN LOOKING IN BOOT, HOLE VISIBLE ON FAR LEFT AT BOTTOM OF INNER ARCH.CAN I REPAIR THIS AREA WITH GLASS FIBRE AS ITS A LONG WAY FROM SUSPENSION MOUNTS OR WILL IT NEED WELDING???