It really depends on what you want to see and how much travelling you want to do. I think you could argue that you have already visited five of the UK's best zoos which are probably also the biggest collections.
Bristol in the west of England is a nice collection, but it's a city zoo, housed in a very small area and you can see everything in a couple of hours. You could visit Slimbridge on the same day, which is a large waterfowl collection (plus a few other wetland birds and mammals) combined with a nature reserve (take binoculars to see rooks, kingfishers and wild waterfowl).
If you stay the night in the area you can go on to Cotswold, near the road to Oxford and London, which is a nice country park collection built around an old house, stable block and walled garden. It's not huge, but it has some interesting species (including gentle lemurs) in good enclosures.
I would certainly consider Durrell if you are interested in rare reptiles and island species; it's not huge - but it's a very high quality collection and their conservation work is second to none, as I'm sure you know. The disadvantage is that you'd need to fly there and back.
Colchester is a larger collection, not too far from London, but the setting and the enclosures are not particularly attractive. There is a good range of species, but only a few are really unusual.
Twycross is a zoo in transition at the moment. It is more or less in the middle of England, not very close to any other major collections. They have some big plans and I think that it will be a better place to visit in a few years time.
My personal recommendations are Howletts and Port Lympne - but then my favourite animals are primates in general and gorillas in particular (PL has gentle lemurs too). PL has a large sloping site (a little like Edinburgh, but in a rural area) with spectacular views across the Romney Marsh and the English Channel and some very nice enclosures for large mammals. Howletts has some similar enclosures, but their gorillas, cats and most of their monkeys are in the wired enclosures that are so controversial in our Photo Gallery. Both of these collections are in Kent, not too far from London.
Hope this helps
Alan
Bristol in the west of England is a nice collection, but it's a city zoo, housed in a very small area and you can see everything in a couple of hours. You could visit Slimbridge on the same day, which is a large waterfowl collection (plus a few other wetland birds and mammals) combined with a nature reserve (take binoculars to see rooks, kingfishers and wild waterfowl).
If you stay the night in the area you can go on to Cotswold, near the road to Oxford and London, which is a nice country park collection built around an old house, stable block and walled garden. It's not huge, but it has some interesting species (including gentle lemurs) in good enclosures.
I would certainly consider Durrell if you are interested in rare reptiles and island species; it's not huge - but it's a very high quality collection and their conservation work is second to none, as I'm sure you know. The disadvantage is that you'd need to fly there and back.
Colchester is a larger collection, not too far from London, but the setting and the enclosures are not particularly attractive. There is a good range of species, but only a few are really unusual.
Twycross is a zoo in transition at the moment. It is more or less in the middle of England, not very close to any other major collections. They have some big plans and I think that it will be a better place to visit in a few years time.
My personal recommendations are Howletts and Port Lympne - but then my favourite animals are primates in general and gorillas in particular (PL has gentle lemurs too). PL has a large sloping site (a little like Edinburgh, but in a rural area) with spectacular views across the Romney Marsh and the English Channel and some very nice enclosures for large mammals. Howletts has some similar enclosures, but their gorillas, cats and most of their monkeys are in the wired enclosures that are so controversial in our Photo Gallery. Both of these collections are in Kent, not too far from London.
Hope this helps
Alan