Things can go wrong , but if the FTTP installation is not completed (and eventually cancelled) that should leave any existing copper pair service unaffected, is it possible that the existing service is unwitting ceased in thus situation , it happens, but as with most things , a few examples on forums like this are not indicative of a general failure, the majority will have their existing service unaffected by cancellation of the FTTP order .
Quick update: Installation all went well. No hassle about the length of the cable. The cable from the External box went up, around, and down the inside doorframe and then fitted into the ONT beside the power socket. So that was all fine.
The only issue I had was that the man said it would take 30 minutes for the internet to get up and running but it ended up taking about 2 hours. I got emails and texts after 30 minutes saying the internet was up so it was supposed to be going, but it wasn't working despite me trying to reset the router and turning on FTTP in the router settings etc. The router just stayed on a solid orange light. What seemed to ultimately fix it was just turning off the ONT at the plug and turning it back on. All has been well since.
Thanks for the help everybody.
@36ULW Thanks for info. I did do some digging and found some information about the length of the cables they use and how they apparently have 10/30/50 metre cables and there is a Premium price where you can pay to get longer cables or something (I needed a sub 10 metre cable so maybe that helped me not run into any issues). The only thing I'd say is I don't know why this info isn't included in the information they sent me in the emails - they directed me to BT website but those webpages had very basic information about the installation and I had to dig around myself to find information about the cables.
@boonjj The fibre cable went up and around the door frame. Just wondered how it looked. Is the white inner so thin you don’t really notice it in practice? Also, is a cover or something put over the hole on the inside where the internal fibre cable comes in from the external box ( CSP)?
@pddcoIn practice I don't notice it, no. But it probably helps that I have a white door frame for it to blend in with. If you have different a different background, say black, it would probably stand out.
Another very minor thing is that the wire is not flush with my waist height skirting, so it sticks out a tiny bit there at that junction. Not sure if that can be installed better or if the cable just shouldn't be bent that much. But it's a small thing, I'm not bothered about it.
There is no covering on the hole of the inside of wall, no. The hole is bit bigger than the wire, you can definitely tell if you look at it. But I'm never looking. It's actually covered by the bottom of front door curtains anyway.