We are renovating a large 5 bed semi and are being advised that the 7-year old Worcester Hi-Flow 24kW boiler (with an 18L delivery rate) won't be able to cope with our plans to add a bathroom and an ensuite; we are also being quoted some high rates (well over 10 grand) for installing a new system boiler with unvented cylinder and new radiators. I recently stayed in a house which appeared to have a combi boiler feeding hot water to the kitchen AND a megaflow serving 3 bathrooms...this got me thinking (having previously thought, this wasn't possible!). Obviously our 24 kW boiler is on the small side for the size of the house, but what is to stop us doing this? We obviously want to have decent shower pressure in the showers and be able to run up to 3 showers at the same time. Also, can you get electrically-assisted unvented cylinders, in case we have guests staying and need more hot water than usual? Any advice gratefully received!