If you are only doing residentail customers do you need to do a risk assessment as far as law goes
A risk assessment should be prepared for all job but not necessarily given to the customer.
God forbid, but should an accident happen you have to prove you carried out all relevant risk assessments and took all precautionery measures.
Remember it's not the type of property your working on that matters, its the fact that you are working at height.
I would suggest making a very basic "template" that you can manipulate for each customer in order to keep things as simple as possible.