There's some sense in what the man above says (there usually is).
I bought a pair of elkskin ropers because I have a problem with lined gloves for ten months of the year. Never use my heated grips...
The sizing info on aerostich.com on the elksin roper page is dead on. Measure the bit of your hand indicated in the little diagram. If you get 9.5cm as the measurement, buy the size 9.5. If you get 9.75cm still buy the 9.5cm as there's a bit of give when you have worn them.
Don't have long fingers - I've got fairly stubby fingers (middle finger about the length that my palm is wide) and they fit where most gloves leave me a half centimetre at the tip of the finger.
I've got a pair of fairly grubby ropers in 9.5 you can try if you are anywhere near Islington...