When to replace vs keep existing radiators
Radiators themselves rarely need replacing unless damaged, corroded, or you're changing the property's heat demand (e.g. adding a heat pump, which often needs larger radiators to run at a lower temperature). A power flush can often extend a radiator's working life significantly cheaper than replacement.
Red flags in a cheap heating quote
A quote well below others is worth questioning — check it specifies a named boiler make and model (not just "combi boiler"), includes a powerflush if the system is older, and states the warranty length. No Gas Safe registration number offered unprompted is a clear red flag.
Three steps to hiring the right heating engineer
First, confirm Gas Safe registration and ask to see the ID card, which lists exactly what gas work they're qualified for. Second, get a written quote naming the boiler model. Third, ask what the manufacturer's warranty requires (usually an annual service) to keep it valid.
Gas fires and stoves — same Gas Safe rule applies
Installing or servicing a gas fire, gas stove, or gas oven/hob is gas work under the same legal framework as a boiler — it must be done by a Gas Safe registered engineer qualified in that specific appliance category, not just any gas-qualified engineer, since categories are appliance-specific.
Carbon monoxide safety
A carbon monoxide alarm should be fitted near any gas appliance, and tested regularly like a smoke alarm. Signs of a potential CO issue include a yellow/orange (rather than blue) gas flame, soot marks around an appliance, or unexplained headaches/nausea that ease when you leave the property — treat these as urgent.
What affects the cost
Cost depends on the type of system (combi vs system vs conventional), whether it's a straightforward swap or a full system change, boiler brand and output size, and property access. Moving a boiler's location, rather than replacing it in place, adds cost because of the extra pipework, flue routing and making good involved.
How many quotes should you get?
Three is a reasonable number for a boiler replacement — enough to compare boiler models and warranty terms without over-surveying for a job that's fairly standardised. Make sure each quote is for a comparable boiler tier, since price differences often just reflect different equipment.
Understanding the labour vs materials split
The boiler itself is often the largest single cost, but labour, flue work, and any additional pipework or radiator changes add up. If a quote looks cheap, check it specifies the same boiler tier (entry-level vs mid-range) as a competing quote, not just a lower labour charge.