Unless you have done a full spectrum analysis you are guessing that the cable will be fine.

VDSL2 uses higher frequencies than ADSL2+ or ADSL, and can be seriously affected by untwisted runs, it will most likely work but you might be sacrificing 5 to 10Meg to a poor cable.

The engineers can be flexible sometimes, but they will not do anything that goes against their install rules, as they will get a bad mark if at a later date you get another visit to resolve unstable VDSL2 and the issue is what they did.

Is there no way at you can pull a CAT5 cable through to replace the RJ11 lead, i.e. VDSL2 modem at master (ideal location) and then router using Ethernet can be up to 100m away with no real impact.

On the back wiring to the master, was ok with ADSL, but am more suspect of doing that with VDSL2, as in time they will relax the speed rules and we might see 60, 80Meg or more from the VDSL2.

Would i just be able to move it afterwards?

well it is your house

At worst you might have to put it back if a fault developed and you needed an engineer visit.

The cabinet is made to measure for the corner of the room and the cable was in-place before the cabinet was put there. So there isn't enough room to put an ethernet cable through.

After roughly measuring the room the router is about 6m away so the RJ11 cable is about 7m-8m.

Well initially you could get an ethernet cable long enough to go round the floor agains the walls while you decide what to do?

It partly depends on money. Maybe 200kbps Devolo Homeplugs, or the new 500Mbps ones might be better in your case.

Well it wouldn't be able to go against the wall because of the cabinet, unless it could be moved an inch from the wall but i highly doubt that.

The alternative it to put the modem at the end of the current RJ11 cable, but reading your post it's unlikely the engineer would do that.

The second alternative is to make my pc wireless and have the modem and router sat in the windowsill.

Nothing stopping you moving the modem after engineer has gone, but be sure to always test with the same setup engineer had originally before reporting any fault.

Physically, what is a data extension kit?

A BT Openreach plug-in cable that goes into the VDSL2 socket of the master and gets a dedicated socket put on at the other end for the modem to plug into.

Ok, Another thing is. What's the process for fttc.

I'm guessing i need a MAC code from my current provider? But i also have my calls with them as well (Virgin).

So when ordering FTTC what do i need to do to get my calls back to BT, or will the FTTC provider do this for you?

Virgin ADSL?

Who do you pay the line rental to, or did you mean that to Virgin as well as the calls?

If Virgin, do they allow you to have other broadband ISPs on the line instead of their own? Several ISPs do.

The line doesn't need to be with BT Retail, but let's come back to that after we have the Virgin questions sorted.