I’ve used RS Plumbing and Heating 01313313827 to fix and service our boiler with success (we’re on oil). He’s a good talker but his works good and prices reasonable.
Have also used Colin Campbell 01313191944 to do some plumbing and was happy with the work and prices. He was just getting into mountain biking when I dealt with him!!
They’re both based on South Queensferry side of town so may depend on where you are