I need to order some hose to link the top of the polo radiator to the expansion tank.
I forgot to measure it this morning and need to order ASAP so its here for bank holiday.
Can anyone remember the ID for the small hose (and cheap supplier for a 2m).
From recollection its around 5mm.

If this diagram is right its 8mm

http://www.discount-cooling.co.uk/Radiators_D10667.html

Mine is like this, but without the 35-32mm reducer (I'd check yours though!!). 2.0 blacktop, polo rad, rover 25 header tank. I tee'd both bleed pipes into a joiner before going to the header tank.

http://www.locostbuilders.co.uk/viewthread.php?tid=177349

ETA - I got my double t-piece for the warm up and expansion tank runs off russbost on here

[Edited on 26/3/13 by me!]

Try your local motor factors