Without a doubt, you will get the same quality for your boiler as if you have paid for it in cash. This is something you shouldn’t worry about in the first place.
How you choose to pay for your new boiler has nothing to do with the quality of the service and the boiler.
Needless to say that you will receive the same warranty protection for the same period and quality regardless of the brand you go with. This includes the Alpha boiler, the Worcester Bosch boiler or the Viessmann boiler.