Beware MJ Quinn engineer
Last year I ordered FTTC from an indepentent ISP. I had a PM appointment slot which I had to take a day off work for. The engineer was from MJ Quinn who rolled up 2 minutes before the end of the time slot and took one look and said, "sorry, your router is incompatible so I can't do the work". I argued with him as I knew my router was good, and even if it wasn't, he would've had to install an Openreach modem anyway, but he wouldn't hear of it, so he logged an abortive visit. I think his shift was ending and wanted to get home to have his tea so couldn't be bothered. The next day I complained and a Kelly Communications engineer turned up the day after and installed it with no problems.
I work for a small IT company and have had many run-ins with incompetent BT/Openreach/Kelly/Quinn engineers, but also there are some that have had some common sense and broke BT's H&S rules to keep the customer happy.