Now then ... I'm really starting to get into photography but am still a novice in many ways. I have a Canon 450D with kit 18-55 lens and feel that I'm limited by the lens somewhat. I have up to 500quid and want a zoom to at least 200mm. Don't mind too much if its something like a 18-200 or 70-300, it will be used in the short term as the only lens so needs to be flexible in application. I've seen the cheapest Canon L series 70-300 at 469 which seems like a good deal, although there are a few others further down the range around the 350-400 mark. I've heard mixed reviews of Tamron and Sigma with no two websites picking the same lens as the best in this group so am somewhat confused.

Any advise would be appreciated!