It depends on where in England you live, but if you're anywhere near Kent, then you should check out sereta cattery. I put Kirby there when we went to Devon for a few days and it is an amazing place. It had pens for smaller animals too (guinea pigs, rabbits etc) and it also had pens for single cats, or up to four cats. They also have very reasonable prices (compared to some places I know) and they do look after your cats very well.
When I was looking at the cattery's, I made sure that the cats in it where happy, that they had experienced on how to look after cats, where clean, made sure the animals got the attention they needed, and made sure my cat couldn't mix with other cats which may have ended in fighting.
If I were you, I'd look for a well known place with alot of experience, and good sized places for your cats to stay. Also make sure that they know about cats, and it would be good if they had a vet around (the place I went to had 2 24 hour vets).
I'd ask what food they would be fed, how much attention they'd give your cat, whether they'd groom them (if needed) and where they would go if it started raining (usually there is a enclosed place for them to sleep).
The cattery I went to asked to see my vaccination papers, but I dont know what other would ask.
I'd book early if I were you because a different cattery we wanted to book Kirby into had been fully booked 4 months in advance!