I would say they are true to size, but a salesgirl at a bike shop described them as "big".
I wear a Large norgie. My Ibex jacket is L, as are my Ibex boxer shorts. On the other hand my Ibex bike capris are M. (only size left in a big juicy sale price). I think I needed a L, but I won't complain too much.
I'm 5 foot 8 and 150 lbs, with looooooong arms. Ibex and Horny Toad are the only brands I've found with long enough arms. Generally I wear size 12 or Large (sometimes XL, rarely M) tops.
Returning things to Ibex is pretty easy. Give them a call and give them your measurements. You might fit a small if you don't have long arms.
"If Americans want to live the American Dream, they should go to Denmark." - Richard Wilkinson