Bomb bay fuel tanks haven't been fitted in decades, and never will be. All the tanks were scrapped years ago when the aircraft were fitted with AAR.
Would fire protection be of any use? Doubtful - with a static air pressure in the bomb bay itself and a dynamic air flow on the outside, anything gaseous or liquid that enters the bomb bay will more than likely be sucked out fairly sharpish - it is not a completely sealed unit. This includes fuel and vapours. Would extuinguishant be effective enough in that situation? If they fire in XV230 was large enough to bring the aircraft down, then I doubt there would be any amount of fire extuinguishant short of that foam stuff used in Demoliton Man that could successfully put it out.