Go for a versatile shoe. In the summer months, most shoe shops have plenty of plain white satin shoes. They're easy to come by and generally not too expensive. The benefit of white satin shoes is that you can dye them after the wedding, so you'll get much more use from them then you thought.
Embellish your feet. If you buy plain shoes, why not try embellishing them yourself? You can buy really pretty beads, clips and feathers from haberdasheries or accessory stores, then simply arrange them in your desired way and attach them with some glue.
Find a cheap shoe stockiest. On the high street there are a number of places to find cheap wedding shoes. Look in the department stores and stores that cater for end of line, end of season, etc. stocks.
Avoid wedding shoes boutiques. Many of the wedding boutiques and wedding dress shops stock shoes but a word of warning, don't buy your shoes from them. Often they're overpriced and you'll be able to find something similar on the high street for half the price. Unless of course, there's a sale on.