D
Deleted member 105431
To the OP I would say Vaillant and Worcester Bosch are the best mainstream manufacturers with a good product range (the ecotecplus 837 and the 42cdi respectively). You will find spares easy to obtain, backup very good and most engineers will be familiar with them. Remeha's spare parts and backup service is a country mile away from these two and the build quality and some of the components aren't as good quality (gas valves for example).