Indeed, I'm ever grateful for the multitude of responses and unending advice. :J

Aye, I've come a cropper of the black sludge before, well at least my carpet has. And it wasn't even me doing it then... the plumber we got was a bit of a lummox and when he was taking an old radiator down from the attic spilt the sludge remnants on the stairs carpet.  :C

I've taken rads off the wall for decorating behind, but have always replaced the existing one, so with fitting a new one I want to get a match as close as possible 'cos I don't want to have to bend or shift the pipes any more than I have to. Lots of towels and old paint trays are your best friend when taking them off.

 

And take the opportunity to put fresh corrosion inhibitor in the new radiator.

Damn fine idea that man.

Well, it's easier than faffing around in the attic if you have an open system and much easier if you have a closed system.