Procedures to starting up freelancing

Hi there im new to this site

im finishing my graphic design course in the uk down in the south west in july. i'm currently work partime at a signs workshop designing, making vechicle signs ,banners etc..
I will be going into this fulltime in july.

But this isnt really the job for me long term, and want to do some freelance work from home in my spare time to build up my portfolio in flyer,leaflet, design, as this is the type of work i enjoy
it will only be small work for a while to help me gain confidence.

How do i start up? i havnt got a clue, iv researched and found i need to be registerd with Vat and Tax? but have no idea on what exactly to do. As i want to be correct and do it all properly.

once im registered is there anything else i need to do by the books for everything to be legal, i dont want to miss out anything and get trouble with the legal procedures or sent a huge bill.

I basically want to offer a design service , maybe advertise on ebay? as one possibility and set up my own portofilo sight.

can anyone help me and guide me to the steps

Many thanks
Becki