I'm sorry my Answer wasn't quite thoroughly on-target. I may have overlooked the fact that USA information does not help you in the UK.
The camera definitely has a problem, I think. Though whether it is a matter of defective design coming out, or just a commonly occurring 'breakage' in this model or line of camera, I cannot say.
puts the matter interestingly, that the autofocus tends to 'hunt' in an unstable way. Autoadjusting autofocus may be a mistake in design, perhaps, in that it is only driven to change in response to certain changes in central sharpness in either a way that is too 'broad' i.e. has too broad a range of bad focus before it readjusts (and thus can stay in noticeably wrong focus for a while) or ruled by an algorithm that is too approximate... and this might be improved in future versions.
Or your camera may be 'broken', as I said. I'm inclined that way. Sending it to Canon UK for repair is the only way to settle that issue though.
Canon UK and its send-in repair service may be done through information provided here:http://www.canon.co.uk/Support/Consumer_Products/Services_Locator/index.aspx
which has two primary items for your attention, first of all a map with two UK/Ireland-located service center locations on it, secondly a Repair Information link lower on the page.
I hope this information fills in what was missing in my earlier-offered Answer.
If this answers your question adequately, please rate my Answer - favorably this time, I hope - so that I may be paid for the work I have done on your case. Thanks.