BT has announced that it is switching from its analogue to a digital phone service by Christmas 2025. This means new (free) connection equipment is needed and, unless it’s very old, you’ll be able to continue using your existing telephone equipment.
To answer your queries, a demonstration vehicle will be at Ickenham Library on 17th and 18th November 09:00-14:00. That’s in Community Close, UB10 8RE. No need to book, just turn up.

This is the only one in the whole borough.
More info here:
https://www.draytek.co.uk/information/blog/the-end-of-analogue-phone-lines-pt2
Follow this link to see how to set it up
https://www.bt.com/help/landline/digital-voice–how-do-i-set-up-my-service-

However if you do not have broadband, this change will be delayed  for a while.