I swear by Roeckl gloves. They do do a proper leather pair for around £39 so a little more expensive than your ideal, but I love their Chester gloves which are under £30 for their summer weight and a little over for winter version - they are synthetic leather, but I get a great feel on the reins with the summer weight pair I own. Might be suitable?
I had a pair of black Roekl ones that were gorgeous - ok, not leather, but I certainly couldn't tell the difference! They weren't the 'normal' Roekl ones though, I think they were £25 but that was a few years ago
They aren't fully leather but I love the mountain horse gloves with the leather palms and crochet back. I swear in them for everday riding and they don't make my hands cold!
Chester Jefferies - you can buy direct from their website. They are handmade in U.K and are the most gorgeous leather - it is Pittards leather so gives grip, but is still ovely and soft. Wide range of styles, colours, etc - start at about £20 for leather palm/fine knitted back, full leather 'The Competitor' is about £40 (very nice showing/dressage glove).