Declaring earnings to the taxman

I don't have a website, but I'm a youtube partner and I earn money off the ads. Since the UK tax year is coming to a close, I'm probably gonna get my door beaten down and be tortured by taxmen unless I declare my income. I have a few questions...
HOW do I do this?
What forms do I need?
Where do I get them?
Do I need to register as self-employed?
Or can it be classed as a hobby?
Do the IRS also need to know about my income from work?
(I'm assuming they do as I'm already paying tax on it once and would rather not pay twice.)
I'm currently unemployed, but my work is on and off but, when I'm unemployed, do I need to tell the social services people about my earnings from adsense?
If so, would I give them an average figure? (Since the amount varies per month)
I was earning money last year, before the end of the tax-year, but was under the impression, the tax was being automatically deducted. Should I mention this? Will I be fined?
If I can't answer all of these questions and any others I think of here, is there anywhere I CAN get the mall answered before the end of the tax year.
Also, the I know the tax year ends on my girlfriends birthday, so if someone could tell me the exact date, you'd be saving me from a potentially awkward situation there.

 

For the start, since you arent aware of the process involved, i suggest you talk to a auditor or lawyer with respect to filing taxes. Taxes are delicate matters and if you make mistakes unknown to you, it will get more difficult.