Thanks guys
Deano they are butt welded .
Ive done them before with spot welding the flare behind the original panel and it made blending more difficult and they are more prone to flexing and cracking the filler .
I prefer to butt weld every 20mm but doing one weld one one side then moving to the other side for the next then stopping every couple of welds to spray the panel with cool water .
The aim is to avoid warping and have the 2 panels sat as flush as possible reducing the amount of blending/ filler required .
You can buy the inner wheel arch extensions from magnum but i made my own , make sure these are fitted and all welded in place as they help to keep things rigid and straight .
However you fit the rear arches they are a total pain to blend if you intend to prep yourself , i spent maybe 2 weeks getting them perfect so if that time was in a bodyshop i dread to think what it would cost unless im just slow....