Thanks Cody for the time and effort, much appreciated as costing can be a black art sometimes.
I've been working part time for 2 years now and have tried all sorts of "systems" but have never gone to such detail, generally I itemise the job and then use GGF (General Gut Feeling) based on other jobs (and the location/client type).
My big tips for you all are:
1. pay yourself well - you'll do a better job if you don't have to rush;
2. explain to the client what else you can do - I've found that many clients don't realize that their problem can actually be solved, and would prefer to deal with just one person;
3. provide solutions, don't just provide "take it or leave it" services - customers want results! and don't care what technique you use, so be flexible and do what needs to be done. I recently got a job cleaning a shop front because I said I would have to hand wash with a brush (especially around the neon signs), when the other company only did pressure washing.
4. when working out your pay rate allow for admin time and other non chargable time (quotes, maintenance etc) as well as holidays, sick leave, savings/superannuation. If I was working 40 hours/week I would only charge out 30 hours. If I have 4 weeks holiday, 10 days public holidays, 5 days sick then I have 45 weeks at 30hours/week to earn what a wage/salary earner would have 52 weeks at 40 hours/week to earn. If I think I'm worth $60,000/year, earned over 1350 hours (45 x 30), I need to pay myself $44.44/hour. On top of this is business expenses: fixed - lease payments, insurance, advertising contracts etc. and variable/job specific - fuel, chemical, hire of special equip, equip maintenance/replacement etc. The total is your charge out rate. Keep them separate. While you are the business, you are also an (maybe the) employee, so treat youself like you would an employee (as a minimum).

I think I'll go and read Cody's original post and then put my prices up.

John