Cool, thanks. I thought our lines were about the same length but your down sync rate is 20mbit better than mine so I don't have a hope in hell of getting G.Fast
Are you using the BT Home/Smart Hub? (They're kinda if'y due to the max 2 week restart from BT central which on certain lines DC's you instead of holding the line and resetting the connection, which DLM may rag you over, giving you an ever decreasing speed limit) - Use a third party device if possible instead. I have temporarily switched over to a TP Linke W9970 on recommendation for now, it has kept things smooth.
Any extensions within household? (Minimise noise which might impact your speed, etc)
Might be nothing, but have you checked voice line for noise? 17070 option 2? If there is noise (other than very quiet modem like noises and screeches) you should get BT/whoever you're with to get that sorted. Could help a little. And every little helps. (I went through 2 years of slowly battling each small section of issue until recently when everything was fixed and I got my speeds back).
If you can check for Errors on your line (normally not with the BT Hubs, but with third party devices), have a gander and see if they're a bit high, would normally denote an issue somewhere that needs fixing (which again, may improve your line).
Further info in case anyone else wants to do a rough comparison on stats (but as Jez has shown, that line length isn't everything, the quality of the line is also as important):
SNR Margin (dB) 15.5 6.4
Line Attenuation (dB) 17.7 9.8