Combination boiler
Combination ("combi") boilers combine a boiler heating primary water for central heating with the facility to heat Domestic Hot Water for washing etc.
Most combis also contain components to make a sealed primary system thus requiring the addition of little more than pipework and radiators to make a simple Central heating system. However this simplicity of installation comes at the price of the boiler being a single point of failure in the system, with Central Heating Repairs usually being more expensive than for a system built out of discrete components, as well as a limited rate of hot water supply.
For a discussion of all types of boiler see the Boiler choice FAQ
Otherwise for best combination boiler in 2017 Hassle Free Boilers have compiled a list using their own data here.