Going back to the the original question, it depends on your area and your expectations.
If you can get a higher price, go for it.
Texas said in one post that if you gain all new quotes, then your too cheap, if you gain none, your too expencive.
Aim to be somewhere in the middle.
If you think its worth £6.00, try £7.00 or £8.00 or even £10.00, if new customers accept make that yor average.
If they are existing customers, put them up by £1.00, see how many you loose.
If they go up 20% and you loose 20% of customers you loose nothing, but gain time to find new, better paying ones.
Try and get the best price possible, your time is your asset, thier lack of time, should be reflected in the price.
All the best,
Stuart