Not many years ago while still in I visited the local ATC Sqn with a view to volunteering to assist
Sadly this is not uncommon. I have been invoved with various ATC units for most of my career to date, and ended up commanding one unit for more than two years in the absence of any other uniformed staff...the reception you get as a serving/ex-serving individual varies wildly depending on the unit and the attitude of its staff, and I have seen everything from warm welcomes to regulars/ex-regulars being forced out by jealous/insecure ACO types.
But noone should be put off by this - unsurprisingly, I reckon that ATC units benefit from the involvement of those who are or have been in the RAF. The only way to find out is to try it...at each unit where I have been a Service Instructor (or more, recently, Service Helper - are we being dumbed down?!), I have started by turning up on a parade night and introducing myself to the staff. Don't be put off by the lack of e-mail response...I have found that many of the e-mail addressses/website addresses in the public domain are either out of date or simply not checked regularly.
As to the level of commitment, I have found that ATC units are usually fairly flexible and would rather have a decent staff member some of the time than rule them out by insisting on exact commitments. Good luck and enjoy!