Thanks to all for the help. So, I’ve started today as planned, after doing some last minute shopping and analysis yesterday.
This is what I’ve found (I don’t like buying health stuff online, I’d rather go in main street shops for these things):
Optifast is simply not available without enrolling in a clinic, but from their site and others I figured out they contain approximately 20g of sugar (short for: carbs of which sugar, so there can be more carbs of the good kinds) for 100g.
Optislim doesn’t seem to be available in UK pharmacies or health and fitness stores.
Elle Belle, couldn’t find it anywhere, but I’d probably not use them due to too much carbs (of which the sugar is unknown), and also 500 kcal per serve is too much — I’d rather have 3* 200, or 2* 300 kcal portions to reach the 600 in 2 or 3 “meals”.
Herbalife, couldn’t find it anywhere either, seems interesting: so little calories (so, more portions), but 9g of carbs per 130 kcal means 41g of carbs for 600 kcal — it’ll depend on how much of that is “bad” (quick) sugar rather slow-intake sugars.
Exante shakes, also couldn’t find them anywhere.
In a pharmacy I found this (in all cases, grams of sugar (“carbs of which sugar”) per 100g):
AYMES: 38/100; Slimfast (who conveniently are the only ones to describe portions in ml rather than g, but with some simple maths I worked it out anyway): an incredible 50/100; Boots Slender: 33, 34, 35 depending on flavour; Conplan: 34, 33, 27 depending on flavour; Sculptress: 20, 21 depending on flavour; Celebrity: 30, 45 depending on flavour; Almaseed: 30. Many of these also had very low amounts of protein (which I understand I should be taking to preserve lean muscle mass).
Eventually I settled for 2 products:
from Boots: Sanatogen High Protein, with impressive 5.8g of carbs (0.4 sugar) and 81g of protein for 100g of product, and
from H&B: USN Diet Fuel Ultralean Nutrition shake, similar composition, 55g portions to 200-300ml of water for 200kcal (so I can have 3 a day) and which specifically is described for weight loss and lean muscle preservation, not performance or sport, etc.
I hope I’m doing it right, I’ll keep researching and of course I’ll make sure to also drink lots of water and have my daily 200 kcal of vegetables as per the recipes in the book, for the fibre and the general gut mobility, etc.
I’m pretty sure in three weeks maximum I’ll be trying to do it all with real food though, for more taste and satisfaction.
I was triggered into action initially by “That Sugar Film” (whatch it, it’s an eye-opener in many ways), then by articles by and about Dr. Mosley on newspapers.