I know it’s a bit off the topic of this site, but this was something I recently looked into and thought it might be useful to post it here for anyone searching for a comparison. This is only five different (UK-serving) providers by the way, and the information is taken from sources across the web. It’s not complete but it should give you a rough idea on these providers.
Please note that I was going to add Secpay to the list as I saw many positive comments about them as well… I can’t do it all for you, can I?! However this should facilitate your own research. Do take this chart with a pinch of salt, as it’s really just garnered from scattered and often out-of-date information. Remember in particular that with regards to QoS, everyone has different experiences… I just averaged out the comments I saw made by people on forums etc., to get a final result for each. Definitely confirm everything before you make any decisions about who to use.