I'm male, height 5 11 and in the last six years I've been anywhere between 12 1/2 and 16 1/2 stone several times - I think I must have lost the same 3-4 stone about four times over. The first time I lost 4 stone and got to goal was with SW, but I've done a variety of diets over the years - Cambridge, Lipotrim, WW, Exante, the list goes on. I'm currently calorie counting with MFP which so far I have honestly found the easiest of all the diets in terms of it's flexibility, you can truly eat anything you want, it's dead easy to track as you can scan bar codes and everything is in an easy database (far easier than syns or points!). I'm hoping it'll also be easier to maintain, on the basis that I'll still have to log everything, though that for me is quite a good way forward.
It's an ongoing struggle for me, so I don't have any major advice to offer apart from that I know that my pattern is usually that I lose the weight pretty well by sticking to the rules, maintain well for 3-9 months and then slowly start 'relaxing'. When I see that I can get away with relaxing (eg having a takeaway and not gaining), I up it a bit and then before I know it, it's been a few months and I've been eating two or three takeaways a week, drinking lager and buying chocolate from petrol stations most days! Which leads to a few stone gained. Not good.
So I suppose my only advice would be to keep weighing, nip in the bud any problems as soon as possible (I'm thankful I've only had four stone to deal with rather than 10 stone that some have yo-yo'd with!) and throw away all the clothes that you used to wear so that you notice you need to lose! I have a friend who lost six stone and he has a 'limit' weight at 12 stone that if he hits he has to count everything and get back down to 11 1/2 stone. He then relaxes a little but keeps an eye on his weight. He weighs himself monthly and every six months or so he hits his 12 stone limit and is very careful for a month, weighs weekly, loses half stone then he relaxes (a little!) and the cycle starts again. It seems to work well for him - he's maintained for about 10 years like this.
Good luck and well done on your amazing loss so far. Bet you're really chuffed.