Tim+ wrote:

cant seem to find anything over 2 metres long.

I can see a 400x2200 off the shelf

https://www.mrcentralheating.co.uk/revive-400h-x-2200l-double-premium-radiator-p

I had a custom towel rad from this lot, they make "column" radiators
with any number of sections

https://www.theradiatorcompany.co.uk/product-pages/classic-multi-column/ancona-made-order-collection/ancona-made-to-order-wall-brackets/