i dont know about Islington. I live in Enfield. Do you have a tumbletots near you? They do different age groups, im going to book my son for another course i think, he's 3. What about a music class, or even story and rhyme time at the library, they have these at the same time every week.
I know of loads of places, having been in the baby/toddler group circuit for nearly 8 years
What type of thing? Pre-booked stuff like tumbletots etc or more your drop-in type group?
If you meet up with us on Monday (see other thread!) I can tell you all about the groups I know I'll tell you anyway but need more idea of what you want.