At the risk of drifting further away due to responses to my post I will answer in reverse order:
BossEyed: Apologies, I knew that the Canopus was at Boscombe and did say from memory, mistakenly it appears, that I thought this was used for demonstrating the early nimrod concept before the two that Cazatou mentioned.
Cazatou: Again apologies, I was going from memory from way back to late 60s early 70s and did not remember those two, so I will amend my statement and say no production Nimrod was ever built and put into RAF Service using any Comet airframes and subsequently converted to MR2/R1/MRA4 (though no doubt someone will correct me on this point as well)