OP, verify the heat loss figures you are getting. Some online heat loss programmes are rough and ready. Double checking the heatloss using two different programmes will be a good idea.
I take it you are opting for an unvented cylinder. You are aware you will need to zone the heating and HW circuits. Creating another zone to split sleeping areas from 'living' areas will reduce your bills if during the daytime one part of the house is 'lived' in.
Might be a good idea to check the inlet and outlet temperatures at each radiator with existing boiler to ensure pipe sizes to each rad are correct.
I prefer my clients to be aware of what they are getting and how the system works. You have done well so far. I have a lady customer who bombarded me with questions to finally request a system that she speced. I was well impressed and she is still a happy lady some three years on, with her system.
I take it you are opting for an unvented cylinder. You are aware you will need to zone the heating and HW circuits. Creating another zone to split sleeping areas from 'living' areas will reduce your bills if during the daytime one part of the house is 'lived' in.
Might be a good idea to check the inlet and outlet temperatures at each radiator with existing boiler to ensure pipe sizes to each rad are correct.
I prefer my clients to be aware of what they are getting and how the system works. You have done well so far. I have a lady customer who bombarded me with questions to finally request a system that she speced. I was well impressed and she is still a happy lady some three years on, with her system.