Metro have the advantage of being able to print digitally to Ilford (the company who make film and darkroom papers) bromide papers. All the (un)usual options of gold / selenium etc make a rather nice icing on the cake. Excellent result, but you pay a price for it.
Is it too against the rules to mention Photofusion.org - a small outfit in Brixton, sat above a very nice market, where we print onto the Canson papers (and others), but the Rag platine is a favourite.