I got this reply from Trinity College when I asked them.
But I wasn't sure what to make of it really.
Thank you for your email.
It is our understanding that UCAS points are calculated for non-Higher Education Institution-level courses (e.g. A-level etc.).
The CertTESOL is a Level 5 qualification, the credits it’s listed as (30 credits at Level 5) could be used towards a degree programme, at least 2nd year undergraduate, but also possibly contributing towards 3rd year undergraduate courses too. So, it may be possible that the 30 credits could be accepted by Universities or Higher Education Institutions, but it will be up to the University itself as to whether or not they accept this.
Sector Support Manager - Language
Trinity College London
AMP House, 10th floor
Dingwall Road, Croydon