If you are fed up with Amazon and want to rule out the new Kindle Touch, then yes the Kobo Touch and the Sony PRS-T1 are probably the best two options. Though Waterstone's are reported to be hooking up with B&N to bring a Nook (or Nook like ereader) to the UK, meant
to be released this Spring (though I don't think there has been any further news since it was first reported last year so perhaps it won't be released until later).
There's not huge differences between the quality of the latest generation of touch-screen readers, but I'd say the PRS-T1 is probably a bit better than the Kobo but considering you can get the Kobo for £75 (@ John Lewis), compared to £130 for the Sony....
Things to consider, the Kobo has things like reading awards, book recommendations etc, some people find them irritating but if you like being part of a community it might suit you. Page turns are still iffy and firmware updates are yet to fix them (as mentioned it has the option to tap or swipe whereas the Sony doesn't but it seems to be people who want to tap to turn pages are having more problems), but that apart it's a fine little reader. It's not as easy to buy books as it is with a Kindle but check the Kobo section of this forum, there's often Kobo discount codes posted.
The Sony is probably worth a little extra for the extra quality over the Kobo (but not £50!) and it doesn't appear to have the same issues with firmware updates not fixing little niggles, but a lot of people don't like the glossy facing it has (though a skin/cover can negate that), though it does have a 'bonus' of having physical page turn buttons. There's no great support from Sony, both in terms of physical ereader support or in terms of a decent shop linked to it.
If you are happy side loading your books (downloading them to your computer and transferring them via USB) then shopping doesn't really matter anyway, you can buy from pretty much where you want and sideload (apprentice alf and using calibre can even mean format shifting isn't much of an issue).
For ease of buying books and delivering them wirelessly though, well the Kindle is tops for that, and with the Kindle Touch now available in the UK....
Personally I like Amazon so if I was buying now I'd go for the Kindle Touch, I *think* I would quite like the PRS-T1 but am not sure it's worth the extra money. If I wasn't bothered about Amazon support, I'd probably go for the Kobo Touch. If price is at all a factor, it can't really be beaten, can it?