Ironically small villages got fibre much faster than some of the bigger cities in the UK because there were many different schemes to bring fibre to those communities. Not that long ago I was in a truly idiotic situation where in the middle of a 1M+ city I couldn't get anything above 50mbps, but a friend of mine living literally in the middle of Northumberland in a village of maybe 50 people had 1gbps fibre directly to his house(and very cheap too!)

Ironically London is one of the worst served places. Outside of hyperoptic noone is focussing on flats (MDUs), and inner London has a lot more apartment buildings than elsewhere.

It's because you're in London. I have family in rural Cumbria with full fibre, yet none of the flats I've rented in London have availability.

There are holes.

Sometimes they are caused by property owners not allowing entry into a block.

Eventually those properties will have to be dealt with, but a legal change may be necessary.

Meh, you might be lucky and get XGPON first, at least Virgin is already primarily rolling it out, no idea about Openreach. I'm living abroad and have 350 mbit up by default. It's considered crappy for the area. Max you can get on consumer GPON in UK is 100. It'd certainly suck for you to wait only to get the last rollout of last gen tech