Well unfortunately it looks like I may not be experiencing gigabit FTTP just yet (with a much higher upstream speed, which is what interests me the most). My regrade to 900/110 may have sadly hit a further delay. It was supposed to be processed yesterday as my minimum contract term for FTTPoD realistically ended yesterday (although I was told it was actually the 10th when I called the ISP today, but given the weekend and easter holidays nobody would be around to process the regrade order). I called Cerberus and the person who's managing my order isn't currently responding when I was tried to be put through to them, so I'm hoping they'll call me back later today with some good news. Obviously with COVID-19 delays are to be expected.
EDIT: Got a response, sadly bad news. There's a system issue at BT's end and is currently being raised with the product manager. Well at least I've had an update on the matter haha.