You might want to try the east malling Sure Start Centre. They do free baby massage and yoga classes (you need to book a place). They also on a Tuesday have a free baby and toddler Play group from 9.30 - 11.30, . Also on Tuesday they run a really useful and friendly New baby Support Group with lots of other small babies and Thursday mornings from 9.30-11.30 they do sensory play for non mobile babies. On thursday they do baby signing, and friday they do messy play sessions from 9.30 -11.30 for children from 18 mths to 5 years or for smaller children and babies Friday after 1-3pm is nmessy play. . They do lots of other activities including days out during the holidays and siblings up to the age of 8 are also welcome at all the sessions. The facilities are all new and fantastic as are all the toys and the staff are lovely. They also run Music Mayhem on Thursdays from the East Malling Institute Hall. if east malling is too far out give the a call because i think there is a Maidstone centre as well . 01732 874086. I live in teston and have an 11 week old son (born 14th May) and 4 year old son so like you am always looking for places to go and meet other mums so we don't all go stir crazy on a bad day at home! I've been taking them both to the Syre Start Centre and they love it. Its nice to get good quality equipment and places to go for free! If you want to try the centre or would like to meet up just drop me a message.
There are some great Sure Start centres in Maidstone - a couple in Parkwood region - The Meadows, which does baby massage classes etc, and has an under 1's clinic on a Thursday for weigh-ins etc. There is another one (but I forget the names, as I am rubbish!) which has a lunch time club on a Tuesday - it's off Northumberland Avenue.
I go to quite a few groups, but a lot have closed for the summer hols.