Heatexcel Avis 

Mike from Heat Excel (ANDERSON, Michael Peter Daniel, Dairy Ebon Court Farm, Lower Ground Floor, Ebdon Lane, Wick St. Lawrence, Weston-super-Mare, England, BS22 7Y) provided an extremely poor and unprofessional service.
He initially promised to arrive with the required part. However, after inspecting the boiler, he said he would need to bring the part on a later visit and charged me £120 for a diagnostic. I duly paid this fee.
Despite this payment, no diagnostic report or written explanation was ever provided.
He then asked for a further £280 in advance for the next visit. Fortunately, I did not pay, as he later informed me that he would only be able to return after 10 days.
Overall, this experience was highly disappointing and lacked transparency and professionalism.

I got several quotes to install a new gas oven and Mike at "Heat Excel - Plumbing and Heating" in Weston super mare, provided the lowest quote, including parts, which I accepted, so I booked an appointment. Mike texted me minutes before the appointment to cancel, wasting my week day having scheduled time off for this. He agreed to attend on a Saturday and when he saw where the oven needed to fit, immediately began complaining about the fact that there wasn't a socket for the plug [instead it had been hard wired] and he didn't have any parts on him for this. Then he complained about the existing pipework and said it needed to be redone. And then he said he could get the parts from the shop. (What gas engineer doesn't keep standard plug sockets and copper piping for a standard gas oven installation in their van? Or at least anticipate this and get them in advance?) And then he wanted to do another job inbetween getting the parts because 'that job is near the parts shop' and said he would be back in 2 hours. Letting me down a second time for a scheduled installation because he was ill-prepared this time. Then he texts me that due to having to buy parts he wanted another £35. Then he changed it and texted another £45. When he came back, he didn't have any parts with him and said they were 'in the van'. I asked him why a bit of copper piping and a plug socket cost forty-five pounds? He said, "I've been sitting in traffic for an hour." So it wasn't really for the parts, it was for his inconvenience, or time, "off the job"! He wasted my time cancelling the first appointment, my time by coming ill-prepared to the second appointment, and tried to raise the price from the original quote for additional parts that should be standard within the quote for installation. When he left he said he could smell a gas leak and refused to return. An immoral and unethical sole trader. If you live in the South West, you have been warned. Avoid him like a gas leak!

Update
Gas services confirmed no gas leak. Go figure.