This form will work out the true annual costs of a permanent employee (in the UK). Just edit the numbers already in the cells. The yellow cells are automatically calculated when you press the buttons, values entered in these will be overwritten. Note that the lower buttons re-run the upper calculations as well but not vice versa.
I've tried to give reasonable figures for costs for a senior electronics engineer position but every company will be different. With the default figures the cost comes out as £50/hr, similar to the rate charged by your garage to service your car and similar to Full Circuit's typical rates. Plus, of course, you would only be using Full Circuit as needed so the net result is in fact a lower cost.