There have been some excellent BBC documentaries over the past couple of years, my understanding is that the advent of ICBMs and anti aircraft weaponry meant that (once they had taken the U2 out) the V bombers became more vulnerable - they started off painted white for high altitude ops in the early 60s and then it was decided they should get camo paint and be flown at low level. They weren't designed for this and performed poorly so rather than renew the airborne platform, they decided to change tack with the Navy and join up with the US in terms of development of a pooled resource.