I have used Thames Gas for 4 years in a row for CP!2 landlord certificate and boiler servicing. I've never had a problem with them due to the same engineer visiting the property. However this year a new guy attended the property. He found several 'faults' and replaced one part at an extra cost of £100 on the spot. I'm still unsure if that part genuinely needed replacing as he never showed me the old part, I just had to trust this man. As he didn't have parts for the 'other issues', he told me he would email with a quote for the work and would have to fail my gas safety certificate until this was done. I still had to pay for the failed gas safety certificate even though I was due for the remedial works. The quote emailed was over £300 including paying for a brand new CP12 safety certificate. Other parts were none essential for the CP12 to pass, however Thames gas said that unless I had all of the works done, they would not pass boiler for the certificate. I asked for a breakdown in parts and labour and again they insisted that this was not possible and should I not wish to carry out all the work then they would not help me and leave me with a potentially unsafe but working boiler. Needless to say I didn't use them ever again. I have since called out another engineer who happily applied, for free, insulating tape to the boiler (the reason for the boiler not passing the gas safety certificate), he also told me that the parts Thames Gas wanted me to replace was absolutely fine and didn't need touching. Avoid this company, they have gone down hill and will rip you off at any given chance!