Slightly longer to arrive than originally told but once there a very affable chap who fixed our immediate problem, but also made clear underlying issues that might lead to further, more expensive problems down the line. Chap explained the workings of the heating system in good detail and answered my questions very clearly. I have a far better understanding of my system now than I was left with by the original installer. Four stars only because I'm left with the worry of knowing we're going to have to spend a lot on upgrading the system in the medium-term future. Not his fault, of course, but not quite peace of mind, either.