I can strongly recommend the man who maintains my Vaillant boiler:
Integrated Heating Ltd
We've been getting ours serviced by Annie for the past few years. She's good, thorough and reasonable. Her number is 07813963965
I've been using Annie as well and find her reliable
I’ve used A&P Gas (aandpgascontractorsltd.co.uk / 020-8802 6969) for boiler servicing — and installation — for many years; they used to be in Green Lanes then moved to Enfield, but the team’s pretty much the same.
A & P Gas serviced my old boiler and did a fantastic job installing a new boiler/hot water/tank and pump this autumn - highly recommend
I agree. A&P Gas are brilliant and very reliable.