Yep, go for at least one size larger then you need, maybe 2 sizes and also wear an inner glove...I bought a pair of Sealskinz based largely on recommendations of forum posts here last year. After initially being impressed (they are quite flexible & easy to use throttle / brake with them on), I have subsequently found them to be largely ineffective in colder / wetter weather such as we have had recently and they have been a slightly disappointing purchase.
If you are going to buy a pair then I completely echo other members comments about purchasing one size larger than you think you will need. I downloaded their hand size guide, printed it off & I checked my hand against it. My hand appeared to fitt comfortably in the middle of the large zone, so I confidently ordered a pair of large gloves. When they arrrived the gloves were way too small, I had to send them back & get a pair of XL ones. My hands are actually quite long & slim and the xl gloves are a reasonably tight fit.