I'm not too sure to be honest, where do I have it from?
You should get a NI number otherwise you are paying emergency tax (the highest possible)
With the number the tax inspectorate will work out what tax bracket you are in and you pay less tax and get more into your hand.
You can also apply for tax back, if you have been on emergency tax.
(If it is still the way it used to be?)
You are an E.U citizen and can legally work in Britain.
Check your current contract, it usually has a part in it where it states you should give one months notice, meaning you give a written statement stating your intentions to leave, it is polite to do this.