Thanks guys for the comments. I feel better already! I did in fact go for a short run (3 miles) after posting the original thread. I felt great. My legs felt fresh, I was chilled and I truly believed that all the Ben and Jerry's ice cream I had eaten at the weekend was just a figment of my imagination!
Anyway, I'm now fired up for the 'long run' at the club tonight. Bring out the cream cakes!