Courses:

Every Tuesday and Thursday evenings in London:
The North London Esperanto group offers free Esperanto classes at the beginner, intermediate and advanced levels twice a week near Highbury and Islington tube station. For more information please visit our homepage.

Duolingo to learn languages for free:
https://www.duolingo.com

lernu! (multilingual website that provides free courses):
https://lernu.net/en

Esperanto in 12 days:
https://learn.esperanto.com/en

Complete Esperanto:
https://esperanto.org.uk/store/product/28-complete-esperanto

Gerda Malaperis:
https://esperanto.org.uk/store/product/33-elementary-course

It’s a course disguised as a novel. The first chapter is very easy and then it gets progressively more complicated. New words and grammar points are explained along the way.

Free course in Barlaston (south of Stoke-on-trent):
https://esperanto.org.uk/events/lernu

The Esperanto Association of Britain (EAB) organizes free courses regularly. They are ideal for people who have little experience of Esperanto and who aren’t yet confident enough to try other events around more experienced speakers.

These courses are definitely worth it not only to improve your Esperanto but also to meet other learners from the UK. Some are beginners, some speak Esperanto very well, so don’t worry about not having the right level.