I'm not a huge fan of berets as they don't really suit me & prefer to wear newsboy caps, flat caps or beanies, but they do so suit some people really well. Especially French people with moustaches.
There's a selection of them here, starting from £9.95 excl delivery:
The Borsalino and Jaxons are more expensive, but with both those brands, you get what you pay for - high quality wool and leather bands. The cheaper ones are probably fine though - they're 100% wool. No harm in opting for one of these, then if you like it, investing in a better make if funds allow.
Make sure you read the hat sizing guide before you buy though as it's very easy to get the wrong size (I'm speaking from experience).