As Dzug indicates, bee-keepers are concerned about the possible introduction of diseases and parasites, such as the Varroa mite, into this country.
It should be remembered that, if bees become diseased (or subject to parasitic attacks), it's not just honey production that could be affected. Without pollination by bees, the whole of Britain's arable farming and horticulture industry could be wiped out.
The ban on personal honey imports only applies to travellers arriving from certain countries. You can import unlimited quantities of honey from other EU countries (and from most non-EU countries within Europe). You're also allowed to bring in up to 1kg of honey from a list of countries which includes Argentina, Australia and Canada.
Chris