Preheat the oven to 200°C/400°F/gas mark 6.
In a bowl, mix the cheeses and Hot Wholegrain Mustard together. Cut a slit into the side of each chicken breast, then stuff with the mustard mixture. Stretch the bacon rashers by pressing the back of a knife along the rasher, then wrap 2 rashers around each stuffed chicken breast just firmly enough to hold the parcel together. Season, and place in a lightly oiled shallow casserole dish, cook in the centre of the oven for 20-25 mins. Serve with green beans and potato wedges.