How to leave a company when you feel you have been forced out?

Following my previous question, how on earth do you leave a company that you have felt forced out of? The people who have treated me badly know who they are however, they are acting slightly weird as they have been discussing a leaving do etc...but then on some days they have completely ignored me. I am currently working my notice...and to be honest, I'm not working to my best, I even took a day off sick last Friday as I just didn't see why I should go in. The thing is, because I'm so afraid of conflict, I have somehow almost let everything go and not confronted issues or people. However, if I leave and I don't tell them what I think, then I may regret it, but I don't want to leave with the upper bosses being glad I've gone. I don't want to go down the tribunal route as it's just too much upset and as I live quite far away from work, once I leave it means I can sever all ties with the bloody place....I just don't want to leave all for nothing. Help!!!