Depends on what you normally spend on food and drink ...
When you're backed into a corner because of finances, it's amazing what you can do. We're struggling right now - so much so that I've had to give up CD. I've just done shopping for five days worth of food for four people on £35 - and that's not junk food either. There are times when a VLCD is just out of the question financially and when you've used it as an emotional crutch for so long, believing that it's the ONLY way you can lose weight, then it's easy to be thrown into a tailspin. It's at times like that you clutch at straws: I can understand why Ceri was trying to replicate a VLCD using a cheaper option. But for the reasons explained previously, it just shouldn't be attempted.
I can totally relate to this post. I, too, have had to give up even two CD packs per day on my 1000 plan because of the cost. Three packs a day (and often four 'cos I seemed to need the extra one, most days) cost about double what I used to spend on food. I originally thought I'd only need CD for three-four months. HA HA! How wrong I was.
I am using Slim Fast right now, two meals each day, plus a well-balanced meal and perhaps a snack. I take a good vitamin/mineral supplement and try to stick to around 1000 calories per day. You will not go into ketosis on Slim Fast. Each shake contains around 27g of carbohydrate.
You could lower the daily total to 800 but it would be very difficult to get the nutrition you need in the 350 or so calories you'd have left. You could try three SF shakes and a snack, perhaps. If the snack was high in protein you might be okay. Even then I'd go for the vitamins etc, as a precaution.
The most attractive thing about SF is the comparatively low price. The company did bring out a low carb range but it flopped. I tried the shakes - ready to drink - ugh! But it was much cheaper than CD and vastly cheaper than LL. LT I have never tried.
The important thing is to find a diet plan that suits you, that you can afford, and that you can stick to, most of the time. VLCDs are unforgiving. If you cheat, esp on carbs, you pay a heavy price - literally.
I've never tried WW or SW 'cos I'm not a 'joiner' and would not relish being weighed in public. However so many people find slimming clubs helpful and motivating that you might like to try one. Good luck in whatever you choose.