With £300 you are about £150 under budget for some really cool Sony glass. Namely the 16-80mm Zeiss and the 16-105mm Sony. Both great, but also both £400+...
If you can stretch your budget £50, and 28mm is wide enough for you, then check out the Tamron 28-75 f2.8. Glowing review
here
When I bought some stuff to replace that really rather poor kit lens, I bought:
1. Minolta 50mm f1.7
2. Minolta 28mm f2.8
3. Minolta "Beercan" 70-210mm f4
Each for about the £100 mark. Any can be gotten for around that figure. The beercan, in my opinion, isn't as "amazing" as people say it is. The 50mm is basically my go-to lens for almost any situation. The 28mm is pretty cool too, but just not quite wide enough on the cropped sensor for massive landscapes, unless you do a multishot panoramic.
As dalex said above, dyxum.com has an immense, user generated, review database of every single Minolta AF/alpha mount lens ever made. Well worth having a browse through a few things. That site that I linked to above also has reviews for every single Sony branded lens made for their DSLRs.