dave:
now heres me thinking that after driving for 4 1/2 hours i need to take a 45 min break before i start driving again, but this does,nt stop me from doing other work.
The regulations do stop you from doing other work at this point until you have taken a 45 minute break. Here is the wording from the regulations.
After a driving period of four and a half hours a driver shall
take an uninterrupted break of not less than 45 minutes,
unless he takes a rest period.
Note what it says, it says after 4.5 hours driving the driver shall take a break, it does not say take a break or do other work. On reaching 4.5 hours driving there are only two options available, take a break or begin a rest period and that is it. If you do other work before taking a break you commit an offence.