roar00,
Accommodation - the accommodation list that's currently being sent out is pretty out of date and most of the people on course 220 (July/August) who are planning on renting somewhere have just looked on rightmove.co.uk/spareroom.co.uk, etc to find places. If you're looking for a flatshare with other TATCs, the departure lounge will help you to make contact with other people looking to share, but facebook is just as good.
Start dates - I've always been under the impression that NATS expect most of their candidates to pass the medicals (I have no idea of stats though) which is why I think they try to give as much info as possible when asked about the next course that has available places, etc etc (on the assumption that you'll pass). I have a 6 month notice period, so if I'd waited until I'd had my medical before they told me anything about courses, I wouldn't have been able to start in July. Also, I got asked at Stage 3 if I knew of any reason why I might not pass a medical - maybe that's a factor too?
Finally, when you get your contract, you'll find that even at that stage, your offer for employment is still conditional - this time on security clearance etc - I know my referee still hasn't been approached so I'm obviously not yet cleared...