I don't know what the 'rules' are . £5 for one for a week , under certain circumstances would be a doddle .
If it is being done seriously , ie not expecting wine etc , then just by buying 'on offer ' food , and not expecting half a ton of crap to be tipped down your gullet every 5 minutes , then it would be very easy .
It all depends on the criterion imposed , ie , i can survive on no money at all , albeit on a very different diet to normal .
£5 for 1 week is no test at all really , £5 a week for 6 months would begin to be a test , as many people are likely to find out this year .