I did more reading around the blue tit in yesterday's shot and, according to the RSPB, this is probably aggressive behaviour associated with this little fella guarding his territory at a time of peak breeding activity. He is mistaking his reflection as another bird encroaching into his area.
Anyway, I spent a fair amount of the day restoring some network drives and optimising my storage of files. Amazing how long it takes to move files around a network (It's still going now, almost 12 hours later!). I popped into the garden in between showers, hoping for something interesting to appear. I don't think this applies, but sometimes you have to make do.