Register with Abbott and you should join a waiting list and eventually be able to order on line.
You may be able to order immediately if there is no longer a waiting list.
I used to get mine from Asda but it was a bit of a drive, so ordering on the Internet works well. https://www.freestylelibre.co.uk/
I used to get mine from my local Asda - its a large Asda though (hypermarket sized - Reading) though so had a separate chemist and optician so I got them from the chemist there.
Once I got them on prescription I then got them from my more local chemist so stopped getting them at Asda.