Theory (for the simple tax-free starting point)
Ultimately you'll be looking to make a profit as a company and a salary as an individual. You get a good ballpark figure by considering this aim from a monthly perspective.
Total up your monthly costs (office rental, Internet connection, salaries and so on). You can easily see that you'll need to be taking in at least this figure to break even. Call this your total cost.
Next consider how much work you'd expect to be completing in a month. Let's say you'll actually be doing 5 hours of client work per day (the other 3 hours you're managing email, learning and so on). At 20 working days per month, that's 100 hours. We're not considering each individuals hours, just the total number of hours people are working.
Divide your total cost by the number of hours and you get somewhere to start. This gives you the hourly rate the company charges to the client.
So as a rough starting estimate, consider dividing your total monthly costs by 100 to get an idea of the bare minimum you need to charge per hour assuming you're working on client projects those hours. So long as you always consider each persons' salary in the total costs, dividing by 100 will always work here.
Example
- Office rental: £1000
- Salary for two people: £4000
- Comms (Internet, phones etc): £500
Total cost: £5500
Hourly charge: £5500/100 = £55
So in that example the company would charge clients at least £55 per hour in order to pay for your office rental, comms and £4000 in salaries (to split between the two of you as you see fit).
That's a good place to start. Add on top of this whatever extra you think your clients should be paying for your personal level of skill and experience.
Your clients are essentially paying for your ability to produce an output. You'll clearly need the skills to do this but also the knowledge and experience to make the right decisions so that you produce the best solution for the client.
Your experience may allow you to make better and more informed decisions giving your clients better solutions. This pushes up the value of that which you produce hence raises the cost and the hourly rate you charge.
The extra you add on top may be much greater than the bare minimum. If your work deserves it, and clients can see this, they will pay.
Future planning
Also consider how you plan for your company to grow. You might find the workload increasing such that you need another employee. Consider when you'll need to take this extra person on and how much to pay them. Increase your hourly rate such that you are making enough extra to employ this new person at around the time you need to employ them. This gets tricky but is worth considering well in advance so that you're prepared for the changes that will inevitably happen.