Ds's plan to stick to his school timetable is working really well. He did make me laugh yesterday when I asked him what subjects he'd revised and he said Chemistry, Spanish, PE, History, English and RE. I said 'What on earth did you revise for PE?' and he looked at me funny and said 'You saw me Mum, I put on my shorts and t-shirt and went for a run' 
So he is taking his timetable quite literally, getting up at normal school time and taking his lunch at the usual break time. He likes this because he gets it all done by 3.30 and has loads of down time in the evenings.
They all like to do it different ways and whatever works for them is best to go with. This is the boy that liked to do the bare minimum before and never put in full effort on his homework. It's changed because he's taken control of it but it was touch and go for a while.
One thing that has worked in the past with reluctant homework/revision is giving them jobs to do instead. I've said to him in the past that he can either spend an hour revising or an hour cleaning and let him choose.
I've also taken away privileges, electronic devices and stopped doing favours (such as giving lifts) in the past to try and motivate my dcs to take some personal responsibility.
Another thing that helped was talking about breaking down homework/revision into manageable chunks. Sometimes it can just be too overwhelming to know where to start. All the sciences break down into 3 separate papers, RE has two papers, History has 3, etc. and it's a lot to organise. Revision guides can be helpful here, as the book can be split into sections.
Anyway, just some things that seem to have helped in our house with both A levels and gcse going on this year.
Well done to your dc's Word, it takes some courage and dedication to get through the DofE awards 