The Gas safe register advises that if you are unsure, suspect or just want to put your mind at rest, you should call a gas safe registered engineer and book a gas safety inspection. A gas safe engineer will be able to inspect your existing appliance to certify whether its function has been affected by new building work and certify whether it is safe to use.
Since 2008 In accordance with the law within the UK including the Channel Islands and the Isle of Man all legitimate gas engineers must be Gas Safe registered and will carry a Gas Safe Registration Card. See an example of a genuine gas safe registration ID card in the picture below.
Make sure the engineer is the person on the card and represents the company you have employed to carry out the work. You will find on the back of the Gas Safe ID card a list of competencies that the gas engineer is qualified to work on and their expiry date. You can check the authenticity of the identification card by checking the hologram and the license number.