The B-52 survived as part of the nuclear triad because the USA had a requirement to maintain all three capabilities. It later survived as a high level conventional bomber because the USAF can achieve and maintain the air superiority/supremacy needed to provide an environment it can survive in.
Now look at the UK. We never had a triad and dropped the air nuclear role because we considered Polaris adequate for our needs. Similarly when looking at long range cruise missiles we considered sub launched Tomahawk sufficient for our needs.
In the absence of an organic force of sufficient SEAD/AD etc to provide air superiority, let alone supremacy, the high level conventional bomber role would not be a credible option. Which only leaves the low level penetration role, which needs a target list outside tactical bomber range to justify the cost of running a Vulcan wing - and eats fatigue life at an incredible rate.
So, to be frank, in the last few years of it's life it was an airframe in search of a role. The Falklands notwithstanding.