Victoria,You can add Worcester Bosch to the list. They with Vaillant were always the benchmark brands, though I have heard talk of another highly rated brand coming to the UK market (might begin with a 'K'?), with very good feedback.It is worth taking the time to consider how effective your current boiler has been. Have you been happy with the way it heats the house, or the speed at filling a bath? That might lead you to the same, or a higher power rating.With that in mind, check the paperwork or stickers/markings on the old boiler. There is likely to be a rating for hot water (HW) in kilowatts - 15-30kW is typical.If you then want to gen up on models, the websites for both manufacturers have quite a lot of info if you take your time. There are other factors in selecting a model, but at least you're working from a position of knowledge and you can guide the plumber towards your wishes (some less scrupulous will propose models with the best margin rather than best suitability). Also, if you google model names, you can truffle out trade prices - useful for assessing how reasonable a margin your plumber is making.I would ensure your chosen model has a visible water pressure gauge - pressure loss is a common cause/symptom of problems and a gauge gives you notice. It may even help you get her fired back up rather than sitting in the cold waiting for an emergency plumber.Final point is to consider timer and thermostat. There are some serious systems now, going as far as week-long programmers for both times and temperatures for every separate radiator. You may not want/need that, but something that allows different times for each day, and placed better for viewing is not a bad idea. It can be integrated onto the boiler facia or screwed on the wall (or even wireless). Whatever you choose, there's no better time to sort it.
Richard Hodges ● 5301d