There are a lot of ways to save money when buying a boiler such as:
If you're on a budget, you may not need to buy the most expensive brand of boiler available. Although the more expensive boiler may be more reliable in the long run, if you're tight on cash choosing a more budget-friendly boiler should get you by until you can afford a more expensive model.
When shopping for boilers, keep your eyes peeled for discounts and offers. Even if you don't see any offers online or in the store ask the sales assistant. They may be able to knock some money off or give you a discount on the installation.
Lots of companies offer finance on boilers like this company offering boiler installation in fife
https://www.seanbrownplumbingandheating.co.uk/heating/. If you're short of cash, finance options can help you to solve the problem.