No! No! No! not foam fill never liked it never will, yes it may be a good and cheap idea but it causes no end of problems removing tiles cracked or flaking cause by frost, and makes it a lot harder to detect where leaks come from, Yes foam filled roofing does leak.
My advice is contact your local building conrol office ask about grrants for a re-roof under engergy saving if the loft is not inulated betwen ceiling rafters you may be able to add that too. plus cavity wall insulation.
it's up to you.
bob
September 2009