Hi mate,
Ive been every year since 2003 & its a great week.
We have always gone B&B or self catering cottage as the NI wind & rain is not friendly for camping!
We're not going in 2012 as we're having a change and doing Assen Moto GP instead.
The best ferry route IMO is Cairnryan to Larne or Stranraer to Belfast. We usually get the Wednesday lunchtime ferry from Cairnryan and then the 7.30am ferry back from Larne. Works well for us. If I remember correctly it was £79 return for bike & rider last year through Nutt Travel.
With regards to digs, I would recommend not heading for the main towns as they are expensive. Getting digs out a bit plus cost of taxi's will still work out cheaper.
Anything else you need to know, let me know & i'll try and help.
Lewis