As long as you actually get paid at some time (in line with the National Minimum Wage) statute law has nothing to do with it. (So there are no all-encompassing rules). It's entirely a matter of the contract between you and your employer (and/or the flexibility which the employer is prepared to extend to you within that contract).
All that you can do is to explain your difficulties to your employer and hope that you'll receive (for example) your first week's pay at the end of your first fortnight. Try politely pointing out that you're likely to run out of money for your petrol (or fares) to get you to work if you don't receive some pay earlier than you normally would. (That makes it the employer's problem, as they'd be left short-staffed, rather than yours).
If you've been unemployed for an extended period, this might help:
http://www.direct.gov...ngforwork/DG_10013908
Chris