Different Fibre Speed Estimates form PN/ BT & Sky
There are no such things as promises or guarantees in Telecommunications Land 
Edit: Except in the industry's marketing departments.
Edit: Except in the industry's marketing departments.
Just to add to the other good advice...
1) I haven't used that device, but a LOT of people are having issues with it.
2) I use the TG582n for fibre and although it is a basic router, I find it totally reliable. I have all my port forwarding set up and NEVER need to reboot it. As already said, it will need the fibre firmware, but that should be easy enough to put on. You could try backing up your current configuration then reloading it after the firmware upgrade. Not sure if it will keep the settings (with it being a different firmware), but worth a try. Worst case just reset it back to factory config.
3) See answer 2 above
4) Combined unit is good for clutter, but I actually prefer the separate units. That way I can try a different router if I want, make router config changes etc, without dropping the VDSL connection. Purely a personal preference though.
5) As already said, the red cable is just a standard ethernet cable so you can use a much longer one. You can also have the modem away from the master socket if required by running an extension (or maybe you requested the extension kit in the order). If the installer fits that, it will only be on the surface (around skirting board etc). Also best not to use existing extension wiring for that (as the typical flat cable is more lossy at VDSL2 frequencies as compared to twisted pair).
6) I had a Kelly install. Just be careful and ensure everything works the way you expect before they leave. You should get a MK3 master socket provided tomorrow (I think it has the better filter components inside it). The MK3 master socket has the extra socket on top (RJ11 though think it also accepts RJ45) that is unfiltered for connecting to the modem (it is not an ethernet port). If you do plan on having the modem a bit further away, or just want a neater install, a cable can be kroned in (IDC connections) to the AB terminals inside the socket. This way you don't have to have an RJ11 cable permanently sticking out the top port of the master socket. It all depends on the location of the modem etc for your particular install.
One last thing, the RJ11 to RJ11 cable that is supplied with the Openreach modem is a flat cable. I recommend using a twisted pair cable for better noise immunity. You can pick one up (e.g. Belkin) for 3 or 4 pounds. This is a 'belt n braces' approach, it doesn't mean it will help, but since that cable is often close to power supplies and sockets etc, it gives your connection a better chance.
Good luck with the install.
1) I haven't used that device, but a LOT of people are having issues with it.
2) I use the TG582n for fibre and although it is a basic router, I find it totally reliable. I have all my port forwarding set up and NEVER need to reboot it. As already said, it will need the fibre firmware, but that should be easy enough to put on. You could try backing up your current configuration then reloading it after the firmware upgrade. Not sure if it will keep the settings (with it being a different firmware), but worth a try. Worst case just reset it back to factory config.
3) See answer 2 above
4) Combined unit is good for clutter, but I actually prefer the separate units. That way I can try a different router if I want, make router config changes etc, without dropping the VDSL connection. Purely a personal preference though.
5) As already said, the red cable is just a standard ethernet cable so you can use a much longer one. You can also have the modem away from the master socket if required by running an extension (or maybe you requested the extension kit in the order). If the installer fits that, it will only be on the surface (around skirting board etc). Also best not to use existing extension wiring for that (as the typical flat cable is more lossy at VDSL2 frequencies as compared to twisted pair).
6) I had a Kelly install. Just be careful and ensure everything works the way you expect before they leave. You should get a MK3 master socket provided tomorrow (I think it has the better filter components inside it). The MK3 master socket has the extra socket on top (RJ11 though think it also accepts RJ45) that is unfiltered for connecting to the modem (it is not an ethernet port). If you do plan on having the modem a bit further away, or just want a neater install, a cable can be kroned in (IDC connections) to the AB terminals inside the socket. This way you don't have to have an RJ11 cable permanently sticking out the top port of the master socket. It all depends on the location of the modem etc for your particular install.
One last thing, the RJ11 to RJ11 cable that is supplied with the Openreach modem is a flat cable. I recommend using a twisted pair cable for better noise immunity. You can pick one up (e.g. Belkin) for 3 or 4 pounds. This is a 'belt n braces' approach, it doesn't mean it will help, but since that cable is often close to power supplies and sockets etc, it gives your connection a better chance.
Good luck with the install.