It will depend what your desired spec is?
IE the appliance types in your properly and demand it requires.
This post is best placed with the heating engineers and plumbing traadesmen.
So go there you will get more informed advice, but I would be asking the engineer that you are employing to fit the boiler to offer you on-site advice.
Head for this forum http://www.diynot.com/forums/viewforum.php?f=7
It takes me about 15 min on the phone to find out from an informed owner what their system is so that I can give them a budgetary quotation.
There are many boilers on the market and each has its own advantages and disadvantages.
Generally I recommend one with a five year warrantee. In many cases the warrantee length depends on the installer as many need an installer who is trained by the manufacturer.
Some installers will only fit one make, others like me are not tied to any m,anufacturer and are free to choose what is most appropriate.
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