Sorry I'm going to disagree with all the above, just to be awkward!
When you lose weight, you'll start to hit plateaus - as you're finding now, losing and regaining the same few pounds - and it's because as you get smaller, the amount of calories you need to function per day reduces. So, say for example, when you were 12 stone you were eating 2500 calories a day to maintain that weight, you then change to eat 2000 calories a day and you lose weight. Only now that you're down to 10 stone, what used to be your dieting amount is actually what you need to eat to maintain. So if you want to keep losing weight, you need to go lower. Or exercise more (as per the advice above). Fine, if it's short term - but how long is that sustainable for? How low are you going to have to go when you hit your goal weight? And then what do you do next to maintain it?
Caroline girvan gets a lot of love on Mumsnet, but she's cardio with weights. Also pretty difficult to follow if you have any kind of mobility limitations or just if you're a beginner really. It'll increase your fitness but it's not the most sustainable - you'll 'feel the burn' but that doesn't necessarily amount to a sustainable programme that will lead to a change in body shape. It's not a good programme for building muscle.
It is virtually impossible to build muscle while on a significant calorie deficit. You can get stronger, but that's not the same as building muscle. The word to note is 'build'. What are you going to build it from if you're eating less than you need per day?
My advice would be to have a break from trying to lose weight, and start with building up a bit of muscle. It doesn't mean you have to go crazy with the calories, eating at around your current maintenance level would be fine (if your weight has plateaued, then you're basically eating at maintenance) If you want to grow muscle faster, eating around 200 calories extra a day would usually be about right, and that would likely mean a very gradual weight gain on the scales, if at all (maybe 1kg in a month max) But if you're scared of the scale going back up, maintenance would be fine.
The reasons I'm suggesting this route is - as you've discovered, being 'smaller' doesn't necessarily give us the shape/look we want, but that can be influenced by exercise. Also because once you have a bit more muscle on your body, the amount of energy your body needs to get through the day increases. So whereas before you might be stuck at 10st and needing to cut calories to say, 1500 to see any weight loss, after a few months of strength training you might find that you're 10st 6, but you need 2400 to maintain and 1900 to start losing weight again. And you're no longer stuck with a plateau, or feeling like you're on a permanent diet, because losing weight on 1900 is a lot easier than sticking to 1500. And once you do start losing weight again, you find you look different, because usually what we think of as 'slim/toned' is actually showing a little bit of muscle definition.
Four times a week is plenty for strength training. Twice a week would make a big difference for most people, the biggest thing is consistency. Six months at once a week will be much more impactful than one month at six days a week.
You'll find lots of advice about strength training in the 'lifting support' threads. There's a podcast I'd recommend as well, it's cheesy/off topic in some places but the fitness advice is pretty good - Mindpump. They did an episode called 'why women should bulk' which explains what I've described above, but in much better detail!
Btw the 'protein window' thing is a myth. Possibly a marketing tool to encourage people to buy ready made shakes and bars at the gym. Concentrate on the amount you get per day, consistently, and you be fine.