More progress today for MOT
Welded in new front seat belt mounts and adapted captain seat bases to fit.

Reused original nuts and welded to 2mm plate 50 x 80mm. Cut out rot around old mount point. Fitted 2mm plate under arch and fillet welded in.
Ground weld flush and then fitted 1.2mm plate on top and with part fillet part spot weld tried to recreate the standard finish.

Had to use bigger top plate this side as rot reached further into arch.

Welded 40 x 10 flat either side of seat base to create height to allow it to swivel. Had pre drilled these with 10mm holes for mounting onto shell.
Original front holes opened out to 10mm and new rear holes drilled through.
Made the plate with welded nuts you can see at top of photo to make it easier to fit bolts to inner side of base. Access restricted here as you have to get your hand underneath to fit nuts.Will fit this plate first with mastic, reach in and connect bolts can then drop outer side down and drop bolts through to washers and nuts as these are easy to reach inside the wheelarch.

Better shot of full base. Will use the plate with captive nuts at top. Will use bolts, nuts and penny washers at bottom of photo as these come out inside wheel arch.