Elaine
In principle your PIP would not be affected by your working, but if the DWP became aware you were doing this and they believed that is was at odds with your stated limitations then it could result in your claim being re-assessed.
For ESA, your only option would be Permitted Work, however it only allows you to work for less than 16 hours a week and to earn a maximum of £102. If you exceed either of these then your ESA claim will be closed.
In theory you could close your ESA claim, do the work and then re-claim under the 12 week linking rule, but it is likely that this will result in a re-assessment of your claim and you could lose your SG status or even be found Fit for Work as you will have to explain how you were able to do the work.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems 
