sorry guys been away for a while hope u all well
anyway dulux have a matt whiteemulsion paint encorperating lumatec technology which
reflectcs light back at 2 times the rate of normal matt emulsion
it is also the diamond range which means it washable and stays matt finish
£15 for 2.5ltr cant be bad
hope this helps.

dulux light and space its called.

I wouldn't call that cheap......do they do it in the trade packs - if not it's probably just a bit of typical marketing bollocks.

How much is a huge roll of aluminium foil??

I give up, How Much?

About £4.99 for 20 metres although I am not sure what the relevance is..

According to a quick google, matt white paint has reflectivity of 85-90 percent. If that was doubled you would be well over 100 percent.