I must admit I agree with spunky and skimmin, I equally dont work for less than 100-120, your a business, if the customer dont wanna pay it then **** em, your not doing them a favour, they wouldnt ever do you a favour so dont do them one! I go by this, small job/half a day 100-150, full day 150-200, depending on how hard the half day or full day may be or what the job is!
For example.. if it was a small bog ceiling, maybe 100quid, if it was a ceiling 4mx4m then Id charge minimum of 150 + materials, both jobs would take me half a day, but one job is worth conciderably more simply because its a bigger lid, and if a customer dont think its a fair price getting a perfectly flat ceiling for that then they obviously dont apreciate what you do!
If someone asked me tofill a hole the size of a 50pence piece though, I wouldnt charge them 100quid, I would tell them to stick some filler in it, number of times people ask ya as a plasterer to fill the tiniest of holes when it just aint the best way to do em, cant beat a bit of filler and a rub down some times.