Monarch do a 737NG course
Aircraft Type Training | EASA Part 147 | GCAA CAR 147 | Monarch Aircraft Engineering
so do KLM UK at Norwich
http://www.klmukengineering.com/en/products
I should imagine either of those 2 companies do good courses. A lot depends on the particular lecturer they assign to a particular course.
the CAA does a list of all the JAR147 approved training providers in the UK
https://www.caa.co.uk/Data-and-analy...ing-providers/