you might as well because i suspect its going to take you a long time to make your mind up .Excellent advice. I have just been out boiling the kettle. I have no idea what you are talking about regarding the boiler sizing but I successfully used the kettle to fill a bucket of water. I took this upstairs and tipped it over the head of my other half who was standing in the shower. She can confirm that the temperature was great but the flow rate was a little high! - all said in jest.
I guess this is where I have been going wrong - I am supposed to boil the kettle and work out the size of the boiler for myself. And now her in doors has got involved. She has just suggested using the kettle to fill a bucket of water which we can then tip over our heads in the shower. At least we will know the temperature and flow rate will be good - all said in jest.