Not sure what time it started. I think it was about 12ish when I got back & I saw it. I probably wouldn't have noticed it otherwise as I should have been out all day, but I cancelled an appt I had and came home.
Just got this back from my hosts:
I have checked the server logs and the site itself, I don't see any reason why the site was down or was loading slowly. It was probably due to high load spike. The service did not crash or stop working, hence, i cant see any errors.
Which in itself is a mystery because the first thing I checked was the server load stats which runs live... and it was showing at <1%. As the slowness was for a good half hour, if it was load then surely I would have seen that on the livestats - as would have the first person at my hosts who I reported it to. ?
Anyway, whatever it was seems to have corrected itself without me doing anything, so it will remain one of life's mysteries.