Odd sized radiators

[Roygillett]

I'm thinking of replacing some old (20+years) radiators but the sizes are proving a bit of a problem. I can easily find replacements for two of them, 600mm X 1400mm and 600mm X 1100mm single panel, but there's a also a single panel 600mm X 650mm and a double panel 600mm X 750mm. All the radiators I've found so far come in 100mm steps. Are there radiators that size out there somewhere or am I going to have to get under the floorboards and alter the plumbing?

[DIY]

I am not a plumber therefore the following is only my DIY understanding. As far as I know rads only come in 100mm length steps now. The alternative to altering the under-floor pipe(s) is to fit a slightly smaller size radiator and then make up the size difference with either a fixed length radiator extension, a telescopic rad valve extension, or a straight lock shield radiator valve.