Hi all, thanks again for your replies and just to come back around on this (in case anyone else has a similar issue).
We decided to go for BT as they had a good deal and allowed us to input our post code with no problems. We moved in on 17/01, and our Openreach modem had been installed (indeed, we had seen it a week prior, during our 'new home demo'). Our router arrived on 21/01, and our internet was meant to go active on Friday 24/01. It did not; the router kept flashing purple, rather than blue. When we called BT, they said it should have gone live and so they contacted Openreach. Apparently it was some kind of 'problem with their system' that was causing the lack of connection, and that Openreach would fix it but that it might take up to five working days. In the interim BT sent us out an EE 4G mini hub for free, which worked a treat. This afternoon our internet went live. So I have no idea what was going on on Openreach's end, but we now have fibre broadband 🙂
