Working Time Directive

A quick question.
I know I need a 15 min break up to 6 hrs work, another 15 min over 6hr and up to 9hr and then a further 15min after 9 hrs. Taking a 45 can cover this. How does it work with a very long shift say heading towards 15 hrs? Does the subsequent breaks have to be within 6 hrs?
Eg: 45 min break taken at 5hrs 15 min into shift. Further 45 min break taken 6hrs and 15 min after last break. Should a further break be within 6 hrs of the last break? All working/driving time, no POA?

For a 15 hour shift and ignoring driving time breaks which also count as WTD breaks

Work 6 hours
15 min break
work 6 hours
15 min break
work 2 hours
15 min break
work 15 mins

Cheers Rog