3G coverage map - showing all networks?

Is there a reference map which will tell you which networks cover a specific location. I know each provider has a coverage map on their website but is there a way of showing them superimposed and comparing signals from different networks?

To answer my own question: found a map of locations of mobile masts on the ofcom website which answers my question. I am looking for 3G for home broadband and the only UMTS tower near is with 3 so they will have to be my choice.

However Orange/T-Mobile info is completely out of date because they wouldn't play.