Move away from the cookies, Wayne!!! That's not the answer...nor the bottle of wine I drank to commiserate myself for being such a loser.
I felt like that, every year until I finally got in...6th attempt! But serioulsy..it is shit, and not fair. But it's not going to change.
Honestly, keep trying. Join a club and try and get a club place. I have no hope of getting a GFA until I'm about 60. But there are ways in....also, if you are in a club and someone can't do it.....I didn't say that, I have never known of that happening 
Meanwhile....the smaller marathons are much more friendly....people talk to you! In London, the crowds are what make it, Tower Bridge and the last 2 miles. Honestly...nip to Paris, or one of the other big UK marthons like Brighton for the feel a of a big one. But try the smalle ones..
But don't lose heart....there are alot of us out there, you're time will come....eventually.