I am a size 10 and have several pairs (different makes) of 26's and they fit very nicely I do have a 28 for when I am wanting a slightly looser fit. IMO a size 8 is 24, 10 is 26, 12 is 28 and so on and so forth.
Personally I think if you are usually a size 8, a 28 would be too big.
It always varies between brands.. im a size 10 and for breeches a 22 in Pikeur, 24 in Hac-Tac & 26 in Mark Todd, and the Shires 24 wouldnt even nearly go on, haha..
The really annoying thing is that all the best sales are online and you just dont know what your getting.. :S
I think they vary quite a bit make to make. I tend to only buy Cavallos as I know they fit. I am an 8/10 (usually more 10 at the moment!) and I wear 24" breeches from them.
VC, 28 will be too big. I am an 8-10 and 24-26 fits me, 28 is very baggy. What brand though? Pikeur are very big, Cavallo small and Mark Todd tiny in my experience!
I'm a 10 and seem to be between sizes, 26 is just a bit too tight and 28 is quite baggy. I go for 28 for the sake of comfort but from the sounds of it 26 would fit you.