As a contractor you would benefit from a Contract Pack contract in the following ways...

Contract Pack makes sure that you are protected from dishonest customers.
Contract Pack allows customers to have things explained from your perspective making for a better understanding and working relationship.
Contract Pack ensures that your payment is secure providing work is completed satisfactorily.
Contract Pack gives the customer clear instructions on the course of action to be taken should the work meet a hiccup rather than the customer taking it upon themselves to dictate unreasonable courses of action.
Contract Pack makes sure that you are treated fairly and justly with regard to facilities, access etc
Contract Pack reassures customers that you are not a rogue trader but have a legal framework you work within.
Contract Pack helps you manage individual jobs when you have several on the go at once.
Contract Pack gives the customer confidence in the timeframe of the work, offering transparency in the project.