I'd think about what you want and try to narrow your choice down.
Do you want to walk every day or would you drive (or use public transport)? If you're not walking what is parking like?
Do they have a uniform? Is that something that you like or want to avoid?
What features are important? Lots of outside space? Forest school? Optional extra classes?
Are you looking for something which is just a preschool, or would you be happy with a day nursery that has a preschool room and a baby room?
Do you want it to be attached/ part of a school or do you want somewhere that sends children on to lots of schools? Do you know which primary/ primaries you hope to get into and do they have children going there most years so there might be people he knows when he starts school?
Are you bothered by which sessions you get, would they give you a choice?
If you're doing half days can they stay for lunch and practise eating with their friends?
Does it feel nice when you look around? Are children busy and happy? Lots of their art work on walls, good range of toys, lots of books, a good home corner?
Maybe start with the websites and ofsted reports for your nearest ones. Are there things you like about them- I saw a report for a local prep school which criticised the fact children were freely climbing a tree. I thought that sounded rather good!