Are you looking at preschools or private day nurseries?
I'm a preschool administrator in Swindon and I certainly don't know any community preschools that charge £650 - 800!
Your daughter is entitled to 15 hours a week funded preschool provision from September 2010 onwards. You may or may not be able to get your full 15 hours with one preschool, or you may want to split it across a couple of preschools. Or alternatively, you can offset this against the fees at a private day nursery.
If you want a preschool place then there are a few preschools that will take them when they're 2, but mostly they need to be 3. The good preschools tend to get booked up pretty quickly but it might be worth phoning some and seeing if they have any space for September. What part of Swindon are you looking in?
If you're looking for a day nursery to use immediately, then unfortunately you will be looking at the kind of fees you say, but you'll get a lot more flexibility about times and session length.
One other option could be a childminder, there's some really good ones and they often work as part of a network so your child would socialise with a wide range of children. Childminders tend to be a lot cheaper than nurseries and many of them will let you use your 15 hours funding too.
You may already have contacted the Swindon Family Information Service but if not, then they will be able to give you a list of providers. It's worth looking on Netmums too for personal recommendations.
Sorry for such a long post, hope some of it is useful!