I wouldn't hold your breath about the Regular Army pal; I know some good lads who served x amount of years, completed various tours and The Army won't touch them with a barge pole when they asked about rejoining. Best bet would be like you say, join the TA, mobilise, get a good report and then see how the situation is in a couple of years.
I'm re-enlisting after leaving training about 3 years ago. I applied in October and have my interview 3 next week and my 203 was cleared by Glasgow in Febuary. How long ago did you leave training, as normally you have to wait a certain amount of time before you can re-apply? I guess before you even start the application process again though you need to be sure you want to get back in, and also prove to your recruiter that your worth another go. Be prepared to get a bit of a grilling from your recruiter aswell, because tecnically you've wasted their time once already so their going to want to make sure you're not going to do it again! Anyways I'm sure if you want it enough you'll work your backside off and prove to them your worth another go. Good luck!