I'm interested in getting unlimited infinity 1 when it comes out and I understand its self install and you use micro filters. I currently have my HH4 connected to a socket in the living room because my master socket which is on a wall in the kitchen has no power sockets anywhere nearby. If I have Infinity 1 could I keep this arrangement or does the HH have to be connected to the master socket?

No - with self-install you can connect the HH (which will be a new HH5 for Infinity) to where you want.

As with ADSL you should compare the speeds you are getting at any extension to ensure that they are as close as possible to what can be achieved with the router plugged straight into the master socket. The same sort of tricks as publicised on the web for ADSL (removing the ring wire, checking that connections are good) should work for Infinity as well.