New radiators, pipe centers very confused

[muffindell]

I'm replacing 2 of my old radiators (40 year old) for nice new ones , but I'm so confused Pipe center is 2040mm and 1040mm, yet the gap between the old TRV's is 1995mm and 1000mm.
So I'm looking at 1800mm(1880 stated center) and 900mm(980mm stated centre). What length radiator extension tails do I need to make up the gap without altering the pipework?

 

[Richardthe3rd]

I'm replacing 2 of my old radiators (40 year old) for nice new ones , but I'm so confused Pipe center is 2040mm and 1040mm, yet the gap between the old TRV's is 1995mm and 1000mm.
So I'm looking at 1800mm(1880 stated center) and 900mm(980mm stated centre). What radiator extension tails do I need to make the gap up without altering the pipework?

Chances are your 40YO radiators are an imperial size.
For most modern radiators & radiator valves; add 35-40mm each side of the radiator to the pipe centre, as you've indicated.