Just outside SW18, but Fledglings on the Common, off Chivalry Road, is great: https://thrive.wandsworth.gov.uk/kb5/wandsworth/fsd/service.page?id=luY0ZxRXaiE

[size=100][font=Calibri,sans-serif][font=Times New Roman,serif]Playhouse Playgroup is a wonderful Playgroup in the Romany Scout Hut on Lyford Road. It takes children from 18 months to 4 year.

Its a truely magical place - I'm now there with my 3rd child and in the 9 months when my youngest was growing old enough to go I felt bereft as its such a familiar enrivonment. They also do cooking, football, dancing depending on the day you go which saves you signing up to do that separately.[/font][/font][/size] 
http://www.playhouseplaygroup.org/

http://localmumsonline.com/local-mums/wandsworth-mums/wandsworth-playgroups/

Hi Mums

Do you know of Playdate groups for toddlers in SW18?

Thank you :)