I think I am being a bit unreasonable - just realised my grumpiness with him is probably due to PMS not anything he has done. Ooops.
Anyway, he popped his head 'round the door asking if I had already had lunch or if I'd join him and colleague. I said I had eaten and needed to go to post office so wouldn't join them.
He said "oh, if you're going to the post office, will you buy blah de blah blah as I need them for ebay".
I said "no" 'cause I didn't want to and when he pointed it out it was on the way, I said "no it's not, it's across the road". (true, it is across the road...)
So, am I just pure selfish and lazy or is it ok to just say 'no'.