A long story... If you do a search you'll find lots of discussion of this, especially from around May. The naive view is that it's a genuine attempt by government to reduce our CO emissions (global warming, etc.) by ensuring that more efficient (condensing) boilers are used.
The legislation requiring this is the Building Regulations, Part L, which you can download from John Prescott's site if you're really interested. There are some exemptions to the requirement, if for example you have a flat with a back boiler, but the process is quite complicated.
If you need to find a tradesperson to get your job done, please try our local search below,
or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local