and hello from a fellow Brit now living in Spain. Its great here, there always lots to do, see and learn. It can become a bit of an addiction, but don't worry you are in good company
When I lived in the UK - I did both, as my cat-sitters were not always available. So I can see both points of view
I used the same cattery for over 10yrs and my cats loved it there, the owners were excellent and couldn't do enough for my cats well-being
If you go for a cattery, just do lots of research, most of the good ones have excellent web pages and you can see what sort of accommodation they offer. Ring them up and have a chat, most would offer you a visit so you could see how things work - always good to do as if you only see the place when you arrive to leave them and you dont like it, its a bit late if you have holiday commitments - like a plane to catch
You might also have cat-friends that can recommend one.
Cats do settle into a new environment and they will be safe, fed and cared for but I do understand why you might be worried.
I prefer to have a sitter come which luckily this happens more often than not for me now. The cats know their home, and if the sitter is a family member or a friend then your cats may already know the sitter, which obviously helps
Well I am sure you'll come up with a solution that you can feel comfortable with
ooo and once you get chance do post some photos of you kitties
we just love photos here
Enjoy the forums ....and your holiday !!!!