Any ideas if they can find out through tax codes etc?

I'm currently working as a Graphic Designer 9-5 Mon to fri. I've been picking up a number of design jobs recently and crazy I know, I'm looking at going freelance as the same time.

They are a small firm and my contract says nothing about me not freelancing, poaching etc.

1) Is it registering for VAT I need to do or registering as self employed, or something else tax related?

2) How do I trade, with just my name? I really know nothing about this

2) Will my company know that I'm freelancing? We have no HR dept and I doubt that anything would be in confidence.

3) When I do my tax returns or whatever (god I know nothing) do I need to detail all goings on in my bank account or just whats come in

4) Is it best to set up another bank account for incoming payments and will a standard current account do?

5) any good books or guides to help me learn the terms (apart from here of course) Part of me thinks is it really worth all the hassle

THanks
steve