James was able to squeeze us in at short notice, and Harry fixed our hot water supply issue in an hour for a very reasonable cost. He suggested we may also want a valve replacing to improve things further, but we decided to leave it for the time being.
When unfortunately the issue came back, they weren't available over the weekend but Harry came around early on Monday to replace the valve and now our hot water supply is better than it's ever been!
I'm so happy with the result, and would not hesitate in using Boilers 4 Essex again.