To be honest, I wouldn't bother with any online service. Most big supermarkets do photo processing (from digital media) at prices which are at least as competitive as anything you can find online. Further, if the quality isn't good enough, you can tell them straight away and get your photos reprinted. (Complaining about online services could prove to be far more difficult).
For example, using their 48 hour service, Asda will print your photos for 5p each. (i.e. £10 for your 200 photos, which is the minimum quantity required to get that rate):
http://www.asda-photo...ts_top_Jul2010_v1.jpg
Asda lets you take your photo media into their store, or you can upload your files online. If you do so, you can choose whether to collect from a store or have your photos posted to you. While collecting your photos from a store let's you check the quality before accepting them, home delivery also has an advantage in that you can get 40 photos free of charge. See here:
http://www.asda-photo.co.uk/
Chris