SAR's are a limited vehicle AFAIA although correct me if I am wrong. Standard data may be released but any notes by 'supposed' competent/professional individuals or indeed any data deemed as "Intelligence" will not be supplied to the individual.
Similar to an Enhanced Disclosure where the proposer (Employer etc) is supplied the information (if deemed relevent) from the discloser (Police etc) although the individual is generally (ok always) excluded access to this "Intelligence".
I can only speak from experience viz a viz ... "Detained" circa 1996 ... there is no necessity in Law to arrest nor charge for alleged illicit drug offence[s]. Suffice to say there was no arrest, charge nor caution [yet this detainment has been entered as "Intelligence" and held on record .. lets just say I know this is fact
]. I WAS indeed under the influence of drugs ... 6 Guinness and 3 Jägermeister yet after being stripped searched and subjected to un-necessary attention ... "Intelligence" details me as a possible illicit drug user! I guess 'Dubia' will not be a stop over destination from now on lol! How long before the 'Dubya' declines me entry?!
This has [is] a serious impediment to my consultancy work overall but in the UK banking sector primarily. While I was cleared to assist the Home Office in a technical capacity ~2003 for the mirror (sister) internet backbone project ... such clearance it would seem has ZERO bearing currently. Granted I would not now participate anyway but prior it was part of my employers T&C's albeit maybe not directly.