What is "SEDBUK"?
SEDBUK stands for "Seasonal Efficiency of Domestic Boilers in the
UK", and is an industry standard for measuring and publishing the thermal
efficiency of a boiler. This is so the public can compare the economy of various
makes and models of boiler on the same fair basis.
They have a website www.sedbuk.com, where
you can look up your own boiler, or the one you may be considering buying. Lots
of other interesting stuff (interesting to plumbers, that is!) about boilers
there too. Highly recommended by me.