A few years ago I was in the club office doing the paperwork after a flight when a very polite Scandinavian gentleman called asking for clearance to FL310 or similar!

As I had an A/G licence I called him back and explained who we were - he was very surprised as he thought he was talking to London Mil - never did find out whether it was breakthrough or just a wrong selection.

Something to bear in mind folks,despite listening out before making your call from the air, it's highly likely that you will not hear transmissions from aircraft which are on the ground. Especially so the higher you are.
Irritatingly, the person in the tower and all other aircraft in the air will hear what you have to say, and in doing so, you interfere with ground transmissions.

From the air pilot GEN 3.4.3 Para 2.2 (a) & (b)...
http://www.ais.org.uk/uk_aip/pdf/gen/10304.pdf

"In the case of TWR, AFIS and A/G facilities, communications on these frequencies should be restricted as far as possible to heights uo to 1000 ft in the immediate vicinity of the aerodrome concerned and in any event within 10 nm and 3000 ft."

The official line is a tad unreallistic and show the limitations of frequency allocation. As an ATCO I always appreciate a brief hello from a frendly voice when things are quiet in bad wx (just don't disturb the crossword/countdown/cards etc)

The ILS on runway 26 at Exeter was/is on the same frequency of the ILS at Cherbourg. Several aviators approaching Exeter from the east have drifted out into Lyme Bay as a consequence. Disturbingly, many did not recognise the Cherbourg "ident" and, had a radar service not been available at Exeter, may have arived either in France or the briney!

The airfield on the same frequency as Bourn is Popham and I think we pick them up more often than the opposite. I did once have a very superior sounding Bourn operator telling me I was on the wrong frequency and would I kindly leave their frequency NOW- till I pointed out that I was calling downwind for 26 and 129.8 WAS Popham's frequency. He went terribly quiet- can't think why :-)
The worst one down our way is IofW Sandown that has the French Frequence Club (Unicom effectively) 123.5 as its A/G given where Sandown is situated this is unfortunate to say the least.