Available 24 hours a day, 7 days a week across the south east. Sign up now to stay updated on the latest news and offers! After the call, we send an engineer around to diagnose your faulty boiler and central heating system and we will provide you with a quote to fix the problem. Published: esther duflo, 2017 ". The latest modern condensing boilers run at over 90% efficiency! that’s a whopping improvement on a boiler that’s over.