Put them all up a pound, dont mess about with 50p's, if you lose 10 you will still be earning an extra 390 on the others.
I myself have an enviable problem, the work I have just bought came from a cleaner who is slowly of loading his work to me for retirement (he has given me a fair bit over the last year), he has been a cleaner for 34 years and his prices are incredibly high.
The problem I have is that I will change them to wfp (not a problem in itself), but I will be at least half the time on each job, I will find it very hard to justify some of the prices and fear I may loose some that way.