You cant work 6 hours without a 15 min break. If your taking your 45 early in the day when that finish it sounds like you shift goes on for more than 6 hours so should have had another 15.
Either spread your breaks out more or take them later.
6h working time or 4,5 driving time, needs 45 break. 15 + 30 not the other way around, or 45 min.
Lets say u started at 6:00 u must start your break no later than 11:59, Or if you drove non stop then 4,29 min. Tacho normaly lits up at 4,15 drive time.
Lets say u started at 6:00 and had your 15 min break next 30 min must be taken no later than 14:59. Before 9h working time, or before u accumulate 4,5 driving hours.
Thats all i know. Thats all i need to know on my current job. I finish at 16:30 
Break time is 15 and 30 or 30 + 30 or 45. 30 + 15 will not make 45 and will not reset 6h working time or 9 h time.
U know u had 45 when your drive time on tacho is back to zero. Working time is not shown on tacho. U must calculate that yourself.
Im 99% sure.
Here maybe this will help.
If you put your card in at 06:15 and have a 15 minute break between 08:00 and 09:00 you would need a 30 minute break before going over 4½ hours driving time or no later than six hours from the end of the 15 minute break, whichever comes first.
For instance lets say you accumulate 1½ hours driving then have a 15 minute break at 08:45 to 09:00 (first part of a split driving break), The WTD six hour rule says you must have another 15 minute break no later than 15:00 (09:00 to 15:00 = six hours), however you must have a 30 minutes break before going over 4½ hours driving time so lets say you have the second part of a split driving break (30 minute break) at say 13:00 to 13:30.
Now you can drive for another 4½ hours or work (driving and other work) until 19:30 whichever comes first, if you reach another 4½ hours driving time before 19:30 you would need another 45 minute break, however if you don’t do another 4½ hours driving you would need a 15 minute break no later than 19:30 (13:30 to 19:30 = six hours).
In this example if you finished work before 19:30 and never did another 4½ hours driving you would not need any-more breaks.
Basically:
You must not go over 4½ hours driving time without a 45 minute driving break or split driving break (15 minute break then 30 minute break).
You must not go over 6 hours working time (driving and other work) without a WTD break of at-least 15 minutes.
Driving breaks also count as WTD breaks, so if you have split driving breaks you will probably be able to arrange them so you won’t need any 15 minute WTD breaks.
If there’s anything you’re not sure about please feel free to let me know and I’ll try to help 
regards, Ken.
edit: I should make it clear that if you always start at 06:15 you could only work past 19:15 three times between weekly rest periods, that’s because you can only work for 13 hours from the start of the shift to the end of the shift (06:15 to 19:15 = 13 hours), this can be extended to 15 hours three times between weekly rest periods.
POA stops the clock though yeah?? Eg start 6am, have 9am-10am down as Poa you can carry on till 1pm!!
Well I hope im right anyway…