Although in the embryonic stages of building up my CCing business and not quite in the £100 per league yet I am finding that, apart from doing a great job, the most important part of VFM is just talking to the customer.
From the first telephone call, to the quote in person, and onto the job, you keep reinforcing what you are going to do for them, advise of any potential problems (to disassociate yourself from cowboys), and then show them you have delivered what you said you would within the limits you set out at the beginning.
I find that talking allows you to show your expertise and become their friend for the day - something which I am sure all you experts do anyway.
I've seen many customers who initially winced at the cost, going ahead simply because the other quotes didn't bother to tell them what they were going to do, and, in the end paid a tip.
Talking and doing a great job is all that matters for me - I don't care how short a time it takes.