When you order lenses online, another thing to consider is shipping costs. All the companies on the price list yesterday have free shipping within the UK. Make sure your online provider offers the same.
A further consideration is whether they have the item in stock. This information could (and should) be provided by all the online shops, but they do not do so. I say that you should start demanding this.
Finally, while looking around, I noticed that Contact Lenses has a forum, which is a really nice idea and very informative.