Greetings all. Just to chime in, as a new TT user from the UK. I was also disappointed to find that my new Go 530 was unable to transmit direction over FM - especially as the Owners manual still states that this is an option.
As for it being a law in the UK that prohibits FM transmission, that info is way out of date. The law was changed on 22nd November 2006 to allow the broadcasting of personal FM devices in the UK. This was promptly followed by a huge rush of FM transmitters (good and bad) coming onto the UK market.
If TT are still using this old chestnut as an excuse to anyone, you can politely point out their error! Furthermore, I heard a rumour that the FM transmitter facility was only temporarily removed due to some bugs in the system and that we may well see its return in due course. I certainly hope so!