ATC Fam Flights don't happen nowadays, more's the pity. They haven't happened officially since 9/11, but sometimes individual captains will exercise discretion if they feel you are to be trusted.
UK rules were changed circa 2002/2003 to allow ATC to be carried, with various caveats and requirements for example, a formal approval letter from the airline Director of Flight Ops.
With that change in place to the regulations, UK NATS have had a reduced national programme up and running since the end of 2003. This is often supplemented by local agreements with other carriers. In either case, they all take a bit of organising and paperwork, but they can certainly happen if the individual makes the effort and is happy to cover the expenses, and the time off, from their own resources.
The main problem is that most carriers limit the flights to maybe one or two a month and only during the winter season so there are not many seats available to a staff of 1000 or so.
Some in NATS do still claim we can't do fam flights but that is usually down to them not having accessed or read the blurb which is published in staff notices, or (more likely) their unit managers not 'advertising' the facility.