Extreme Improv

I went along to the show 'Extreme Improv' at Phoenix artist centre in Covent Garden last week.
There were 8 comedians doing sketches based on input from the audience mixed with prearranged themes for the sketches, like having to follow on your part with the next letter of the alphabet.
The show ran for an hour and had the whole audience in stitches throughout the hour.
It is different to a stand up show or comedy play but I found extremely enjoyable. It's the first Improv show I've been to but would like to see more.
Does anyone have any suggestions for groups to go and see in London?
thanks

Not sure this should be in Sitcoms. But anyway the first port of call should be The Comedy Store Players, every Wednesday and Sunday. Then there's the wonderful Austentatious: The Improvised Jane Austen Novel, every Monday in Fortune Theatre. Also there's a dedicated improv club called Hoopla in London Bridge, all sorts of different impro shows.

Ahh. My mistake sorry.
These look great, thank you very much! I'm looking forward to seeing them.