I felt really weak around midday, so decided to try some flat coke. So far I've drunk a can of that, and no vomiting.
I've had so little energy I've been in bed since 4am (when not doing the above).
My guess is it's a norovirus-a-like thing. Lu's also got it, but lucky for her no vomiting.
Bleugh. Bleugh. Bleugh.