If you are recieving funding from a research council, are you allowed to supplement your income through employment. Is there any maximimum. Thanks in advanc

Yes you are allowed to earn extra money, from things like demonstrating & teaching, although this should not exceed 6 hours per week (unless you are teaching in a school or technical college where you are allowed a full day). If your work is not related to your PhD then you need permission from the Research Council to do the work and you will need the backing of your supervisor.

Of course many PhD students have evening or weekend bar jobs or other casual labour. I would doubt that any of these people have applied for any official permission.

You should also remember that unless you earn over your personal tax allowance (about £4800) on top of your studentship, you will not be charged any tax.

yu can actually earn a lot from demonstrating - I get £8 an hour - compared to bar jobs etc., that is a much better way to earn some much needed dosh.