Forgive me as a non-pilot, but I think there is much in what Hangarshuffle says. I found the individuals at Yeovilton Air Station superb, and as an engineer I tended to know the maintainers, but across the road in the RN’s Aircraft Support Executive is where I always thought the SHAR demise started.
I was project manager for some of the major avionics in the late 80s/early 90s and they just didn’t give a toss. Just as Blue Fox radar was going out of service at a rate of 3-4 sets a month (total about 55 sets), they authorised a 10 year spares buy. That denuded the Blue Vixen radar funding, just as it was entering service. Thankfully, it was superb kit and exceeded reliability targets, but we wondered at the sanity of it all. Millions had been spent on MADGE Phase 2 (NFIMS/MDDLS) and they just suddenly declared it all consumable, with £100k LRUs scrapped for the sake of a £20 repair. (Not helped by a rating reversing a 4 Tonne truck over the MDDLS kit). One irate BoI president phoned me to ask why only one squadron was fitted. I was surprised they managed that. He went ape when told the truth. At one point, I loaded 25 scrapped TWTs (£15k each) in the boot of my car, took them to EEV at Witham and recovered 19 for under £500; which helped that one squadron stay serviceable for a few months. Then they told EEV to just scrap the (MoD-owned) vacuum chambers as they wouldn’t pay for their upkeep. The same happened at Thorn-EMI Varian on the radar magnetrons. The waste was astronomical and no matter how hard you try, the beancounters are always going to spot ambivalence about an expensive capability. No doubt there were other reasons, but I just thought the RN, at a certain level, didn’t put up too much of a fight. Very sad.