Kent Trading Standards (part of Kent County Council) have an online tool that lists vetted traders. You can search for a specific trade type based on what you require and geographic location. The scheme, "aims to prevent financial abuse, stop doorstep criminals, and protect residents, especially the vulnerable, from criminal and rogue traders". Simply search for 'KCC Trading Standards Checked' and it will take you through to their website. The Trading Standards website also contains lots of other valuable advice and information.

KCC Community Warden Jason Gordon has considerable knowledge and training around this area and delivers excellent inputs to community groups about the signs to raise awareness. Both he and I are always happy to be contacted about any concerns you have or if you need advice but cannot make recommendations about which trade personnel to use.  Jason also has a considerable number of leaflets and other printed literature about rogue traders which he can provide to you if you wish. 

If a tradesperson approaches you or knocks at your address offering to undertake work always remember the following. It is your address, and you have control over it; if you feel intimidated close the door and ask them to leave. Do not feel pressured to be polite as your safety is the priority; The work they are offering to undertake is unlikely to be an emergency otherwise you would have noticed it yourself, and so you can take your time exploring which trader you wish to use; Utilise the above tool to contact a vetted and recognised trader, request quotes so you know the agreed price in advance and always request an invoice/ receipt. Enquire about the guarantee on their work should you need to call them back.

Consult with family and friends if you are uncertain about any building work being undertaken. Often, they may be able to provide you with advice and scrutinise the quoted price. Again, there is no rush, and if a tradesperson is pressuring you about time and it makes you feel uncomfortable, it should be a red flag. 

In summary, take your time, control the situation, use the tools available to you to research the trader, seek advice from trusted people, and scrutinise the work to be done and the price quoted.