Hmm. Would of thought my suggestion was still do-able, with a little back ending. What you really want to hope for is an Openreach installer, not one of the Kelly's/Quinns contractors.

Ideally I'd like both the modem and the router to be located in the study, although as you say, we could sight the modem downstairs at the master and use the existing CAT5 to connect it to the router in the study.

I guess we couldn't move the master socket though as our burglar alarm is wired into it at the moment and it wouldn't be very easy to extend that cabling.

Yeah I made sure i gave a filter to the alarm company when they connected it up, so its sitting inside the alarm control box.