So i have successfully straightened the jbl basket I made a jig out of 25mm mdf to mount the woofer on, the basket was bolted face down with 5 bolts, I made a bracket/hook out of metal to hook under the lip where the gasket was, this was then held in place with some small G clamps, this hook was connect via a chain to a 2lb hammer. i was then able to yank on the hammer in the desired direction to tug the bend out, It took quite an effort and number of pulls but its perfect now. I have had to replace the gasket. Tried to upload a couple of pictures but no luck, I resized to around 40kb and less than 1000 pixels wide.