Tosh01:
The other driver has told me that if I split my driving time with a 15 min break within it that I then have to take the other 30 mins break within the scheduled 4hrs 30 driving time;
Ask him to show you the regulation that says that ? 
From 561/2006
Article 7
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.
This break may be replaced by a break of at least 15 minutes followed by a break of at least 30 minutes each distributed over the period in such a way as to comply with the provisions of the first paragraph.