Excel 2007 : Calculating basic hours worked, between a time range and premium hours worked

Hi,
I am trying to calculate the hours worked for a Service Engineers time sheet, my problem is we travel and work on weekends and through the night, so our basic pay is between 07:00 and 18:00, the rest is overtime, unless it is travelling time, see below for the companies explanation on this.

Site basic hours 07.00-18.00 Monday to Saturday
Premium rates 18.00-07.00 Monday to Saturday
Sundays and Bank holidays at basic rate x 180%
Travel hours Monday to Sunday basic rate x 80%

I have attached the spreadsheet so it will make more sense to you, I have filled in the Premium hours and Site Basic hours manually, these are the cells i want to automate.

I will also need to add a tick box for each day to say if it is a bank holiday or not and then include the x180%

Any thoughts on the matter will be gratefully received, if it can even be done in a formula?

Roy