Congratulations on your new baby!
Suggest that you avoid the general mayhem of toddler groups and seek out things aimed at small babies.
If you are in Muswell Hill, I recommend the Pages Lane Playgroup at the Methodist Church, Pages Lane, Muswell Hill. They split out by ages so your tiny won't get run over by toddlers in plastic cars.
Tiny Talk for babies under 6 months
Campsbourne Childrens Centre also has a group for under 1s, and baby massage.
Campsbourne Childrens Centre
When it comes to Baby Massage, you could try the YMCA as oops suggests, although as it is a drop-in it can get busy. Tuesday 2-3pm. Alternatively, you could try Baby Massage lessons at Yoga Junction, Weston Park (Crouch End):
Yoga Junction timetable
If you want to meet other parents, can I recommend that you join your local NCT group, then you will get invited to teas with other mothers in Muswell Hill. You don't have to be a member of the NCT or to have done an NCT ante-natal class to join the list, though it is nice to support the charity. Just drop an email to your local contact person (who will be a volunteer local mum, not an employee of the charity) and ask to join the list.
NCT Haringey
And if you are going to soon be interested in exercise, then there is Pushy Mothers in Highgate Woods and something similar in Finsbury Park. Also exercise with Kit is good, in Hornsey Vale community centre on Mayfield Road in Crouch End(yes you can take your baby) Thursday 1-2. You probably want to wait for your six week check first though.
There is tons on, don't hesitate to post again if you want pointers.
All the best- it is the best rule in the world to promise that you will leave the house every day! It saved my sanity!