T-Mobile UK are the second carrier to announce that they will be offering the HTC Hero, after Orange UK threw their hat into the ring earlier. Unlike Orange, however, T-Mobile will be renaming the Hero; it will be known as the T-Mobile G1Touch, to better link with the original G1.
The specifications of the device are, unsurprisingly, exactly the same as with the Orange version. Orange claim to have exclusivity on the "graphite" finish, so we can only assume that what you see in these photos is a more generic gray.
The T-Mobile G1Touch will be available from mid-July (no word on whether that means it will land on Orange - who say "early July" - beforehand) priced free as long as you take out a minimum of a £40 ($60) per month contract. That will get you £225-worth of credit to be spent on calls, SMS and MMS messages, together with free on-device data access.