Hi ritzi,
Sorry to hear of your difficulties.
On the taxation front. Have a look at this link on help with low pay:
See if any of it matches your circumstances.
Perhaps it would be worth paying a visit to a welfare office.
You can also get an under 26 youth card. This will allow you to get similar discounts as students on some shops, hostels, cinemas & travel. [broken link removed].
Is there any way that you could re-establish contact with your family? Or could you talk to a family (aunt or uncle) or other family friend? You appear to be in a very serious situation.
Prehaps another AAMer would have better knowledge of these matters?
D8L