Aftermarket breadvan seats

Hi polo people. Hope you're all safe and well. 

I'm hoping to get some guidance on some seats i have for my breadvan. 

Managed to score some Seat Cupra seats that have been adapted to fit a mk2 polo. They fit great and are nice and comfy. 

Only issue is, the pins underneath are on the wrong side. They still fit onto the runners but the adjusting handles and pins, were on the other side. 

I have a plan that i'm hoping will sort it out, using steel tubing with correct internal diameter, welded onto the other side as a pin guide.

Question is, if i remove the adjusting arms and bolt the seats into place, is this okay as i know you can get fixed seats? 

I read that if a seat is fixed and not intended to move, that will pass an MOT. If i just bolt it in place underneath on the runner, would that be acceptable or would i need to change the mounts as well to bucket seat style ones? 

The cupra seats i have are from a 3 door so do flick forwards for access to rear seats. 

I do have some steel tubing that i was looking to cut down. It's the correct internal diameter to fit the adjuster pins so could try and weld that on as a guide tube. 

Any guidance or xp would be appreciated. 

Thanks for stopping by.

Keep safe.