Thank you for letting me know. These are the people who make a difference.
So, to conclude this thread, I received a telephone call on Tuesday from a very nice Irish man from BT. He apologised and said he'd been in contact with OpenReach and they had scheduled an installation for 25th August.
He also had a small 4g router and SIM sent out to me, which was a nice touch.
So, out of the blue, yesterday (Saturday 19 August) at 0730 OpenReach turned up early and did a full installation, and by 0830 I had 500 Mbs of internet goodness being piped into my flat.
So, a big thank you to all who got involved and helped me with this.
Thank you!
@Deadmonty many thanks for posting the update, I've passed on your thanks to @StuartH who helped you with this.
Neil