I don't remember too many specifics offhand, but I can help with a few things. One food item that was and remained quite popular through the eighteenth century was ginger bread. This was a byproduct of Britain's imperial connections to the Caribbean, which produced a great deal of sugar and related products like treacle (molasses) and rum, as well as ginger. Ginger bread can also be seen as a kind of holdover from the medieval period, in which cuisine frequently emphasized exotic and often (to us) overpowering combinations of spices like pepper, cloves, and ginger. This broader, cuisine-wide emphasis on spice diminished through the eighteenth century, but remained in some areas, including gingerbread (and later, in fancy biscuits, but that's nineteenth-century stuff). (See Mennell, All Manners of Food).

Other important elements of eighteenth-century food deal with the predominantly rural nature of Britain at the time. Because the bulk of the population lived in the countryside, food reflected to a much greater degree than later the rhythms of agriculture and the rural community. So, there's a much greater emphasis on seasonal foods and preservation. One example is rose hips, the fruits of rose plants. As with any fruit, they would all become ripe at roughly the same time, and people would eat them fresh but also put considerable effort into preserving them. As preserves (which could be done in different ways, such as with sugar), people could eat them through the rest of the year, a vital supplement to the much leaner days of winter and early spring, when wild foods in Britain are scarce.

Another example of a seasonal food is seed cake, a loaf of brown bread with caraway seeds and some other spices. The "seeds" suggested both the caraway, but also the occasion at which seed cakes were traditionally made--the harvest, when wheat and barley were harvested. In the nineteenth century, with rapid urbanization and industrialization, these seasonal foods largely left the British diet, only to be replaced--at some delay--with much more industrialized, mass-produced and -marketed products.

A good comparison of eighteenth and nineteenth food in England is Andrea Broomfield's Food and Cooking in Victorian England.

Have you seen the show The supersizers go?. It's a historical show where two people live life in periods through eating the food. Its entertaining and this episode is from the Georgian period.

Here's some cooke books online;

The Cook’s and Confectioner’s Dictionary: Or, the Accomplish’d Housewife’s Companion by John Nott, cook to his Grace the Duke of Bolton (1723)

The Universal Cook and City and Country Housekeeper by Francis Collingwood and John Woollams, Principal Cooks at the Crown and Anchor Tavern in the Strand, late from the London Tavern (1792)

:EDIT:

Just read your title it's for a competition. You'd probably want to make something spectacular. Check out the french celebrity chef Careme, who cooked for King George the IV. He's noted for making architectural desserts, like the croquembouche. I linked his cookbook below;

The Royal Parisian Pastrycook and Confectioner from the Original of M. A. Carême By M. A. Carême