Not a bad idea but I can see problems that might occur with that. If you rent out your facilities at say a tenner an hour and Joe public comes in intending to do a simple job on his vehicle that he thinks is going to take 2 hours and then he has problems and can't get the job done as he needs additional parts that weren't previously planned for but can't move the vehicle because it's in bits until he gets the said parts. Your facilities are then tied up preventing others from using them and Joe public with the car in bits doesn't want to pay you for the 10 hours (£100) he's had because he could have got the "simple" job done for £60 at a garage in the first place. How do you then get the money out of problem customers that end up taking far longer than they originally thought?