Hello SKOL,
If the "incident" is one where UK ATC has filed paperwork on i.e. an Airprox, Mandatory Occurence Report such as a level bust or similar then the Safety Investigations Officer at the unit would request the Telecommunications section to make a copy of the tape and listen to the tape for the purpose of making a unit report.This report would be sent to ,amongst others, the UK Safety Regulation Group.
Tapes (the original magnetic tapes or digital if thats how it is these days) are impounded for varying lengths of time (no fixed length) until it is deemed the investigation is complete or in the case of an accident for a substantial time after the event.(litigation may ensue some considerable time after)
If nobody requests the tapes then they are erased after 30 days and put back in the loop.
As an individual, to the best of my knowledge other than a supena (spelling?) or filing an ASR you would have no process to ask for the tapes to be held.
You could approach the Safety Officer at the unit involved but then if your incident is maybe a dispute with an employer then the Officer would probably feel obliged to make the same info available to said employer on the grounds of being impartial.
However.
Not all incidents are brought to the attention of ATC in house and often an incident (broad definition there) may be brought to the attention of the unit via an airline company safety officer. The same process is (or was)followed as above.
The concept of recording RT is quite simple, safety ,and what we can learn from and improve on as a result of someones incident. Plus of course they are a legal document.
The cassette tapes made by TELS are used to transcribe the tapes for the unit investigation but these transcripts are in no way legal documents.
There is a dedicated department which does the official transcriptions when required.
Hope that gives a bit of an insight to the process.
Please bear in mind my experience in the field is a few years ago and I stand to be corrected by anyone with more up to date info.