Stanny,
tell your dad to read some of the comments on this forum if he needs reassurance that you wont get a visit etc. I am a couple of threatening letters ahead of you, and I'll be your your early warning system as I would get a visit first (which of course will not happen). I've got myself into the mindset of looking forward to the next nonsense letters, and G24's pathetic attempts to intimidate people into paying up what is not legally due. keep us up to date.
Just for your info so you get a sense of timings and frequency of letters etc - my alleged parking event happened on 16 Dec, the first letter sent to me called 'Contractual Parking Charge Notice' was dated 23 Dec, which offered a reduced charge from £75 to £50 if I paid within 14 days of the issue notice letter. Of course I didn't pay (as recommended by all the friends on this forum), I got my second letter on 12 Jan, telling me that the full £75 was due (cheers G24! but I will be ignoring this letter and all others of course).
I should be due for another 'fierce' letter soon, so will keep you posted. CAG members say that a max of 6 letters are sent, then they dry up completely. I'm looking forward to collecting the whole set! lol! It's just not worth it for G24 to keep on paying postage etc, and as Scooby Doo says, why would they risk going to court only to lose their case, which would cost G24 even more money. They will just move on to weaker victims.
Please don't pay G24 any money!! If it makes you feel better, put the money to one side and treat yourself when the letters dry up.