Working
Your passport will normally be stamped with either restriction on working or prohibition on working. If you have a restriction you will normally be able to work for up to 20 hours a week. You will also have to register for national insurance (a tax levied on earnings). Do check with the UK Home Office on the exact requirements the latest rules. A good place to start is the UKvisas site, linked to at the bottom of this article.
The Department for Employment has a telephone helpline +44 (0)114 259 4074 for international students seeking advice on work permits, or contact your college.
Most students will be granted a restriction on working. However, if you are prohibited, it is important that you do not seek employment. The British authorities take a very serious view of this and there can be severe penalties. You can apply to change your status, contact your college if this affects you.
Grants and funding
As an international or overseas student you will not normally be eligible to receive funding from the local government, nor welfare benefits (although there are exceptions).
However, there are some grants and scholarships available to overseas students from the British government and educational trusts. The British Council has lots of information on who to contact and it is worth investigating if the government in your country or other funding bodies can offer anything.
It is important you consider this before travelling to the UK as many scholarships and grants will not be available to you once you have arrived.