Before you choose a CCTV professional, you could take a look for qualifications and memberships from the Institute of Sound and Communication Engineers
, Confederation of Aerial Industries
, NICEIC and City & Guilds.
Before choosing a professional, you may also want to ask for examples of past work, which could include images of different types of CCTV that they have installed in the past. You could also look at their profile page on Bark, and Bark can show you CCTV installer reviews from past customers too, as well as examples of work that they have completed. This might also help you get some ideas for the kind of cameras you might like and the level of security you need for your property.