I need around 2.5m of 25x25x2 box section to finish the chassis. I don't trust the B&Q stuff and don't need 6m from FH Brundle...

Anyone got an off cut they want for beer money?

I have used B&Q for 25mm box. Cuts and welds just like the real thing

I thought I read on here it was low grade and not good enough for a chassis.

I could be making this up though..

There's the metal supermarket in Southampton where they'll cut whatever you want and are quite reasonable

Metal supermarkets are excellent, they will do some pretty good cutting work for free if you need it too.