Preheat oven to 200C/400F/Gas 6.
Smear the partridges well with butter and wrap each one with 2 slices of pancetta. Place in a roasting tin and cover with foil. Cook in the oven for 30 minutes, then remove the foil and roast for a further 10 minutes or until the juices run clear. Leave to cool slightly.
Drizzle a little oil over the bread and toast or chargrill on one side, then rub the toasted surface with the cut garlic and sprinkle over a little oregano. Slice the partridge and layer equally onto the toasted bread with the mozzarella, tomatoes, sunblush tomatoes, basil and olives.