Lots of good answers already. It's basically personal preference, plus the consideration of whether you need your gloved hand to do anything (whether you load with it).
I personally load with my left hand for air and 3P shooting, so my current glove of choice is the Gehmann 465, but they're all really variations on a theme. Best thing to do is get into a shop and try as many on for fit, materials, etc (if you're down at Bisley ever, the NSRA Shop there has a broader range. Not sure why they don't do more with the Aldersley site - as you've found out, they've got the facility there but aren't quite investing in making it a proper target sport centre with a decent shop or anything).
"A fear of weapons is a sign of retarded sexual and emotional maturity." Sigmund Freud
Shooting is my meditation
I saw a used Anschutz Style 125 glove on fleabay, and in a rash moment put a bid on it. I immediately regretted it but thankfully have been outbid anyway. Whew!
There is a book I know I need to buy instead; so the money would be better spent there. (I am just out of the habit of posting cheques, PayPal and bank transfers are just sooo easy).
I will not be abusing my stock - as a mechanical engineer of many years, I have a cunning solution in mind for increasing the fore end depth. This also means more time for me to tinker - 'sheditation' is my form of meditation!
The other alternative is to screw an extension onto my ulna, but this may limit some of my fashion choices...
Too many guns, or not enough time?