Ahaa, the reason I ask is a friend of mine lives in an ex-MOD property near Huntingdon. They managed to get BT infinity in the end but their problem was that most of the phone lines in the area were aluminium.
The best way to go forward IMO is to use this checker
https://www.btwholesale.com/includes/adsl/adsl.htm
If you put your phone number in there it should tell you what cabinet you're connected through, and from there you can work out if its likely to be upgraded to fibre.