I'm getting started but unsure of where to perform

http://www.lionsdencomedy.co.uk/comedycarcrash.html

Not sure about this listing, but worth a trawl

pen%20Mic%20Comedy/" target="_blank">https://www.list.co.uk/events/whatpen%20Mic%20Comedy/

There tend to be quiet a few in London last time I looked. You will need to phone around. Best of luck.