Of course the usual warnings should come with any topic like this
In the UK banks don’t see your so-called “credit score” when they query a credit reference agency, they just see your credit history details and decide on their own internal score based on their current appetite as a lender. You can compare that to the US where the FICO score is much more universal and used by banks and therefore more important.
So while a credit score from any of the UK credit reference agencies might be interesting to see (and see how it changes), it isn’t something lenders see and can be very different from one agency to another. Not all banks report to all agencies, and not all lenders query all agencies which leads to very different outcomes when you apply for credit with one organisation compared to another.
The credit score always fluctuates (regardless of the data on the report) to keep you hooked and make sure you check back every month, so you can get exposed to their “offers” which is how they make their money.