Thanks everyone. I do feel a lot better today, and actually slept last night (the first time for a week). Possibly because I'd bumped myself right back out of ketosis with a banana, OJ and nuts, mind you! I'm going to take it very easy today, throw a handful of berries and some chopped nuts on my breakfast, and a few cherry tomatoes on my lunch and see how I go. I'll not take risks, I will head to A&E if I have another extended episode, or if I have pain, or faint, but otherwise I'll review after the holiday weekend. It won't be my thyroid medication because it takes much longer than a week for the need for any changes to show through, plus I know they were fine only 10 days ago - might be different if I had any thyroid of my own, but given I don't, medication needs are very stable after a long time.
BWIW, thanks so much for your reply, it's good of you to take time out of your holiday to keep an eye on us - hope you are enjoying Malta. I will try the berries first, and have the toast if I need it - bread of any sort tends to give me the munchies, I've never understood how people can stop at one slice, whereas berries are more easily portion controlled for me, so if they work, they are a better bet for me. But won't hesitate to have it if necessary.
Herman, that's interesting, it describes exactly what happened and I feel kinda reassured having read it. Thank for finding that. I'm thinking that I maybe do need to do as they suggest about a more gradual cut down. I was reflecting last night that last Sunday I probably ate 400 gems of calories over the day - a bit higher than my usual, but not excessively so. Then from Monday onwards I was eating about 15gms. I hadn't been counting, but when I worked it out I was a bit taken aback by the degree of change I'd made. It probably would have been more sensible for me to have eased into it, but I decided to join on the spur of the moment.
Hope everyone has a good day and manages to eat their BBQs without the buns and pimms :)