I just tell them 'That's £50 an hour + VAT + transportation... Would you like to make an appointment?'... Most say no, but those who don't are indeed worth the hassle.
Thats my "base" fee- £50 an hour. After a while you get a base of customers.
I cherge those a LOT less- to line my pockets a little but to keep their custom. There's alot of competition round these areas.