I can only comment on questions that I have direct experience of.
OR left my existing extension socket and wiring in place, but I don't know if anything is still connected or not as it's no longer needed for my Broadband connection and for phones as they're all DECT.
They will run a 'Data Cable' from the Master Socket to where you want the Modem positioned. The cable is up to 30-Metres. Don't know if this presents a physical problem if longer than this is needed.
I suggest you use their Hub and consider an alternative Router later. There are lots of postings on these issues if you research this Forum.
OR turned up as promised and install was about an hour and quite painless.
Allergy Advice: This post may contain traces of Meerkats.