Radio Caroline is on 204.640MHz on London North, London NE is the lowest frequency 195MHz. I don't think the range or building penetration will vary much over the Band 3 channels though.

I am in a block of flats and get good reception of all the London MUX also Surrey and Herts, of course in a car results may not be so good. In the 1980's we used Band 3 for London Buses comms with around 10 base sites to cover London, it had good mobile reception, but was analogue trunked rather than digital.