Having to get a new hot water system because your boilers break down (often at the worst time!) can be pricey, but to get the lowest prices you should search out some online prices.
Your choices for a replacement boiler would be:
Combi boilers are for smaller properties that don’t need to use a lot of hot water at the same time – fed directly form the water main they can produce instant hot water, but because they don’t have a storage tank, the flow of the water can be compromised if you turn on multiple taps at the same time.
System boilers, however, do have storage tanks and can supply many taps at once – the drawback is that if you use too much at a time then the water can cool down a bit whist the tank refills andn heats up.
You could use a system boiler in conjunction with solar thermal panels