Its like being back at work! Except i dont have a rack of boots in front of me to help you with your choice.
Bear in mind that leather is the most naturally breathable material. Gore-tex is only a membrane which allows sweat through, but not water in. If you were to choose, go for a full-grain leather boot. I usually offer customers the choice of fabric boots if they are v.casual walkers (dog walking etc).
If your looking for brand names i can give you lots, but its best to go to a shop, look for a full grain boot, and try it for size etc. Ask the shop assisitant the details of the boot (goe tex etc). A good thing to have is a sturdy sole. Ask the shop assistant for something to tread on with the boot on, the harder the sole, the more comfortable it is. the problem with it being hard is it can get heavy. There is a type of sole called a "Vibram" sole. Its a company that make soles for shoe companies. They make high-class, light wienght, very strong soles. They have a yellow logo on the bottom of boots.
Meindl really are at the top end. Full-grain, strong leather waterproof and breathable. you really cant get much better.
Berghaus also do a good boot. But the seem (in my shop anyway) to be mostly concentrating on their fabric boots.
Gelert do a range of budget leather boots, but you can really see the lack of quality in the leather.
Hi-tec the same as gelert.
A leather boot takes longer to break in. If your in cardiff, come into my shop on sunday and i could go through them all. If not, ask your shop if it would be ok to wear the boots round the house before buying, just to make sure.