The closest Mikvah (30 mins walk) is the Central London Mikvah:

21 Andover Place
London, NW6 5ED
Tel: 020 7372 7237.

Other mikvaot are available in Golders Green (3 stops on the Northern Line Edgware Branch / 15 minutes by car).

Northwest London Mikvah
40-42 Golders Green Crescent
London, NW11 8LD
Tel: 020 8731 9494

For details of other mikvaot in the London area visit mikvah.org.uk