Please see the I.C.C guide https://icatcare.org/advice/choosing-a-boarding-cattery/ 

Your cat's safety should be paramount, are there double doors and a safety corridor to prevent escape and is the building secure?
Is the owner a passionate and knowledgeable cat lover, running the cattery as a full time job or is it just a sideline to provide extra income in addition to their occupation?
Is it a cats only establishment, or are barking dogs present which can unsettle and frighten many cats, especially in new surroundings.
Is there any provision for extremes in temperature? There can be unexpected days of intense heat in summer which can be dangerous to a cats welfare. Equally, if you wish to enjoy a winter break, you don't want to spend your holiday worrying that your pet is feeling cold.
Do cats from other households mix together? Cats are mostly solitary creatures and mixing with strange cats can cause anxiety and also spreads disease and infection.
Are the cat rooms spacious with natural light? Cats need to move freely and be exposed to natural light. Cats also love looking out of a window.
Is there access to outdoors? Cats appreciate being able to go in and out as they please and experience fresh air and natural scents, sights and sounds, this greatly improves stimulation.
You should always visit a cattery before commiting to booking, you need to be sure your cat will be safe and well cared for.