My question involves workers compensation law for the state of: London (Uniter Kingdom)

Hello,

I was working in a gambling computing company and I have a few questions.

I've been working for this job 8 months and after that period I found another job. I had to give them 1 month notice, so told them that I was leaving, but in this new job they wanted me ASAP, so I tried to make a deal with my bosses if we could agree to end my contract before. I tried to make a deal, but they refuse all the deals I gave them (including do not get paid my last month until I finish my current projects at home for free). So after 1 week I stop going there, and 5 days later I start in this new job.
They said they are not gonna pay me the last month.
The dates are:
- 16/09/09: I give them my resignation letter. They refused to give me a signed copy. So they have a copy but I dont.
- 22/09/09: I stop going there to work and I send a message to the manager that Im not going there anymore.
- 24/09/09: I tried to access to the skype account they gave me to work with them and contact my workmates, but they changed my password. To do this they had to access to my computer (I gave them the password of the computer to give them access to the project files, but I didnt give them my e-mail password), then to my private mail (When you press a key in my computer it access to my work e-mail because the password is saved on the computer), and then inside my private e-mail account change my skype password.
Both (this e-mail and the skype password) they create them for me for work, but they are mine. They are private.
I havent tried to access my email acount because I have not the software required on my personal computer, but Im pretty sure they change it as well.

I'm not sure but I think I have 2 or 3 days of holidays left.

My questions are:
1st) Is it legal that they access to my e-mail and skype accounts and change my passwords??
2nd) Is it legal that they refuse to give me a signed copy of my resignation letter?
3rd) They say to a work-mate that I'm not going to get paid this last month. Is it legal that they refuse to pay me this month?
4th) I used to work 8 hours in front of a computer. I heard that working with computers you have the right to get 5 minutes break per hour. Is that true? They didnt give us permisson to have those breaks. We have cigarrette breaks but they are just 1 before lunch and 1 after the lunch. So our breaks are one 10 minutes break at 10:30, another 1 hour break between 12:00 and 13:00, and another 10 minutes break at 16:00. Is that legal?

The most important question for me is what can I do to get paid.

Thanks a lot,

Dani