Firstly this needs to be a poll.
Secondly, all the guidhall halls tend to be close to everything, although I'm glad I got James Watson because it is the closest to everything and is the newest halls.
Rees halls are catered and are pretty decent, although there are about a 15minute walk from the nearest bar.
James Watson halls are right next to the main bars. Also, you don't really need to worry about halls at the moment - Portsmouth is unlike other uni's and when you confirm your place with them they send everyone their halls application form some time in May (I think).
Freshers week can be whatever you want it to be - for me, and most people it was pretty crazy. Getting to know everyone and enrolling during the day, then getting really drunk and staying out all night - you'll love it.
As for internet access, all halls have 10MB broadband. Plus there is wireless internet about the uni so you can always have a browse in your lectures!
EDIT: Is Pompey your first choice then? Where abouts in London are you from?