All MoT repairs have to be seam welded all way round if it is a patch, if it is a replacement panel, IE; cut out the whole of a wing, sill etc, and are replacing complete part then can be welded as original, ie sills spot welded, wheel arches spot welded, etc (but only if full part replaced not repaired)
The MoT for structure states no corrosion causing perforation within 30cm of a seatbelt,braking,suspension, steering or suspension mounting point
Billy(MOT tester till last year)