Steve,
We have just put most of our prices up at the beginning of Feb, I would suggest that you do it not more than once per year unless situations change dramatically.
Houses under £7.00 went up 50p, above £7.00 went up £1.00, also brought minimum price up to £5.00. Others that we were already getting a good price for have not changed this year
So far we have only lost one customer but have gained probably 20 + new ones since the beginning of Feb, without trying and all at the new prices
If you feel your prices need to go up, then do it, we have increased our daily significantly without doing any extra work.