Depends what you are looking for really - childcare, or just some Nursery education / new experiences for him?
Don't be put off by names, there are all sorts of names (Nursery, Pre-School, Playgroup, etc.), all of which can offer a variety of things.
There are school Nursery classes, and 'stand alone Nursery schools' which will have a teacher in charge, and can have a much higher ratio of children to adults - so, once a dc turns 3, a teacher can has 13 dc to 1 adult (ratio remains the same even if other adults aren't teacher qualified - so teacher can be responsible for 39 dc with two NVQ qualified people. They tend to operate school hours. They tend to not be very flexible with the way they offer hours (eg, all mornings or all afternoons or 2.5 day split)
or
There are PVIs (Private, Voluntary Independent) which can be anything from a pre-prep class at a Private school, to a community playgroup in a Church Hall, or a private daycare business set up in a house in a street, or in a Children's Centre. These tend to be staffed by NVQ qualified people, and (once the child turns 3) can only have a ration of 1adult:8 dc.
The term after your dc is 3, they can get 15 hours funding so if you are starting them somewhere now, it's worth checking that the Nursery takes the funding (as not all do)
As you already go to toddler groups, I'd ask around people there - they will be able to give you the 'lowdown' in your area as to which ones are recommended, but I'd go along and see a few and you'll see how different they all are.