Can anyone recommend a beginner DBA course in London
Ask your boss to get you a pluralsight subscription.

Additionally, read answers from people like Paul White, Aaron Bertrand, Remus, etc and try to answer questions on this site.

Read blogs from sqlskills.com, brentozar.com, mssqltips.com, sqlperformance.com.

Also folks from sqlskills and brentozar are giving inperson training in LD.

Sqlbits event in UK and the videos on it are extremely helpful and don't forget virtual academy from Microsoft.