Windsor and Newton Series 7 Miniature are my favorite brushes, personally. I use a 2, a 1 and a 0 predominantly. I have a 000 as well for detail. Some people do everything with a 2, from basecoating to eyeballs, but I don't trust my brush control that much.
Alternately, Rosemary & Co series 33 brushes are excellent as well, I've found, and much cheaper. I made the mistake of buying the long-handled ones though. It's not hugely clear on the website that they are over a foot long! I poked myself in the ear with those quite a few times.
I haven't used the
GW brushes personally, but they seem to be actually more expensive than the W&N ones, but don't have as good a reputation.
I also have a couple of Games & Gears double-ended brushes which were fairly cheap considering they're essentially two brushes in one, but looking at the ones in the shop they can be hit and miss in terms of getting a quality tip. I use them for basecoating, generally, and for using metallic paints. I don't use my W&N brushes with metallics, generally. I'm not sure why, but I've got it into my head that they're bad for them.
A good idea, if you haven't already got some, is to get some brush soap to keep those lovely expensive brushes in top condition as well. My collection of destroyed brushes can attest to this.
I hope this is helpful. Don't take my word as gospel though - I've only been painting for about a year and a half, so I'm sure some of the more experienced painters can give you some better advice!