I have tried it and one thing I noticed, for Gatwick at least, is that the radio – Gatwick Director – is practically nonstop. It is ok with me, flying alone and with 15 years of IFR time and thus used to machine-gun delivery radio chat, but I bet most pilots will turn it off pretty quick. It is quite distracting and for example one cannot talk to passengers.
Peter wrote:
I noticed, for Gatwick at least, is that the radio – Gatwick Director – is practically nonstop
Agree with that, I turn it that RT machine gun very down but I expect it to be a different RT artillery when they call me up
When I hear radio silence on that freq, I turn volume up: they stopped machine gun and now looking to call me 
I use FMC especially around Manchester, but anywhere it’s advertised as being available. Honestly, I enjoy listening to them.
I listened to Stansted FMC on our way to Duxford and despite being 8am local, it was machine gunning too.
I think you have zero hope to talk to them as long as you stay clear of their area
It’s just a mean to contact an infringer and reduce the mess, not prevent the mess. Plaster on a wooden leg.
Most of the bigger airports won’t give you a service. Yes; the idea is that if you infringe they can call you to get out of there, which should reduce the severity of the infringement. I am told that once your Mode C is verified, the 5000ft add-on becomes just 1000ft. But if you actually went inside CAS you will still get MORd and then busted by the CAA…
My original point was that the radio is pretty busy, distracting, and I have the feeling that not many will be listening to it. It certainly isn’t some frequency on which somebody will just call you up. It is a really busy approach/tower control unit and to get anything out of it you have to have the volume up and listen to it constantly.
You can go with 0012 east and 0013 west they are much quiet on weekends (just don’t use 7000 
)
A busy Approach or Radar channel doesn’t bother me at all.
I usually get the ATIS and set the relevant Frequency Monitoring Code (so ATC may notice me if they are paying attention). Then I listen and check ADS-B in to get a picture of other traffic.
Then I call for a transit anyway.
Unless I have misunderstood Mr Gratton’s “zero tolerance” airspace infringement policy (in which case I’ll be delighted for him to correct me), just setting the FMC with Extended Squitter is insufficient. If I’m flying close enough to CAS to need the FMC, then I’m close enough to need a proper transit clearance.
I don’t tend to use FMC.
I prefer a radar based FIS (aka. Traffic Service in the UK) and/or clearance through the airspace instead.
I have never used one.
Firstly I plan not to infringe. Dedicating my radio and my transponder to a function designed to help a nearby ATSU (who are not providing me with a service) in the unlikely event that I do infringe is not, in my view, a good use of that equipment.
Secondly, while I am perfectly capable of dealing with machine-gun RT, it is not my choice of background music.
Thirdly when it comes to units like Farnborough I do not want to give them the opportunity to try and control me in class G for the benefit of their high net worth traffic.
If in an AIAA I would use a listening watch. I am not expecting a service but it allows the controller to vector instrument traffic, a reasonable proportion of which may be emergency helicopter or medevac aircraft, so not just a HNWI.
Further down the food scale there is IFR training feeding the lo cost zero to hero sausage machine.
Listening squawk should and is viewed as a mitigation in the event of infringement. I have certainly received helpful RT in the proximity of temporary airspace, old style ‘purple’ flights.
