Sadly there is no up-to-date list of courses using SageMath,
it is a good point, and I wish me did maintain such a list.
Regarding textbooks based on SageMath, see the last few posts
to this list:
- sage-edu, 2020-01-21, Karl-Dieter Crisman
And well-known Sage book, now in Spanish
- sage-edu, 2020-01-18, Karl-Dieter Crisman
Sage book in Portuguese
- sage-edu, 2019-12-23, Dana Ernst
Links to Sage-related books
More specifically about the UK, you might check with Fredrik Strömberg
whether he got any replies to his sage-edu post:
- sage-edu, 2019-09-26, Fredrik Strömberg
SageMath educational users in the UK?