Im very confused regarding blackberry services. With T mobile I have to pay 5 pounds a month for BB services.

I will definitely get this. I also plan on getting a pay as you go sim.

My question is do i also need internet as a part of my package to use these blackberry services. All I need is email and BBM

All you need is a BlackBerry data plan. Internet is part of BlackBerry data services.

You won't get "internet service" per say.
The Blackberry services plan will open up the necessary channels for the email & BBM to work.
All other functions that require INTERNET will not work.

Not true Mobihand. As Rambo said above, a BB data plan will give you Internet access and access to RIM services such as email, BBM, Facebook, the BB browser, etc. You do not need any other data add on.