I buy some on eBay - quality can be variable though. For good stuff I go to dots n stripes online. The Quality is brilliant for the price especially her sale stuff. And her customer service is excellent - free shipping when you spend over £75 for example.
And when I felt like splurging I buy from chez ami when they have a 30% off sale. The quality is awesome and the fabric itself is a reasonable price. Shipping however is eyewateringly dear and the customs charges are high. But oh my gosh - the fabric is so worth it. I made my daughter a dress 2 years ago and it'a a bit short on her now but it still looks like new.