Chester Zoo

All I know is that it's cheaper online than buying at the door. Check cereal boxes, as sometimes they have discount codes like a free adult ticket for a full paying one

We’ve bought a membership as we worked out that we only need to go about 3 times in a year to make it worthwhile

I have a membership aswell, it costs around £20 a month for myself, my partner and my step daughter as my little one is still free.
We love it and go as much as possible, plus it gives you cheap members days and access to some other zoos.
There are a few other zoos too thst differ in prices and sizes not too far away, blackpool, ponderosa, Welsh Mountain and Yorkshire wildlife park (they even have polar bears!) :)

Blackpool Zoo is cheaper and you used to be able to use Clubcard vouchers for tickets (not sure if you still can, haven't checked in a while)