You may be talking about Vidotex by Handic Software AB from 1984.

This is what it looks like:

https://i.imgur.com/YJrMrDu.png

I uploaded it here.  I do not know how to use it.

https://file.io/IAy9xxFLthUj

You may also be interested, if you are not already aware, in modern Videotex services with clients for modern platforms:

https://glasstty.com/?p=1

I'm from the US and this is really the first opportunity I have had to check it out since, as you indicate, this is mainly a UK thing, or, if not mainly a UK thing, not a US thing.  I encourage people who have never played around with Videotex to check it out as it is trivial to install and runs right over the Internet.

--- Mystic BBS v1.12 A47 2021/12/24 (Linux/64)