Oh dear - I'm ill. After flying along mid-week - on top of the world (which is always a warning sign!) and doing loads - I'm now over-trained and actually ill.
Always important to analyse how this happens: Wednesday did too much - big bike ride with 2 goes up a very steep hill, Thursday was understandably a bit sore (good, a training effect had been achieved) and then pretty tired on Friday - so sensibly didn't exercise.
By Saturday I was feeling wrong - either hungover or the start of hayfever - but by the afternoon it turned out to be an actual illness - sore throat and general weakness.
It means my big plan to attempt to climb the Burway in Church Stretton will have to be put off until I'm right.