17-50?
Is it that much better than the canon 18-55 IS?
at least it gives you room for a canon 10-22mm or a tokina 11-16 later

it's a stop faster at the short end and two stops faster at the long end for a start, and Canon's 18-55s have never been particularly good examples of the lensmakers art.

No, not had the canon 18-55 IS version, but the 18-55 non-IS kit lens that came with the 400D was terrible. From what I could gather the Canon equivalent of the Tamron 17-50mm with IS is about 3x as expensive, so it wasn't an option, though the Canon is regarded as the best (or one of the best) in that focal range.

As to Simply, the Bastards ignored my requests to cancel the order and shipped it, so I now have 2 identical lenses. I can either return it and have to pay the postage, or hopefully find someone locally who wants an unused decent lens at £245

No, not had the canon 18-55 IS version, but the 18-55 non-IS kit lens that came with the 400D was terrible. From what I could gather the Canon equivalent of the Tamron 17-50mm with IS is about 3x as expensive, so it wasn't an option, though the Canon is regarded as the best (or one of the best) in that focal range.

As to Simply, the Bastards ignored my requests to cancel the order and shipped it, so I now have 2 identical lenses. I can either return it and have to pay the postage, or hopefully find someone locally who wants an unused decent lens at £245

Send it back & then tell them you cancelled the order before shipping & you want a refund on the postage as well (both ways) - dont let them charge a restocking fee - thats illegal - dont take any sh*t from them, just quote some distant selling act as well as the cancellation email (though I normally phone to cancel unwanted sh*t) - unless you bought the lens outside the UK ofc.

I think Canon basically assume that most serious photographers will replace the kit lens quickly and most non-serious photographers wont mind because, bad as it is, it's still better than all but the very best compact lenses. They got pretty heavily slated for having the worst of a bad bunch when it comes to kit lenses, which I think is why they've tried a bit harder with the IS version.

Thats true & without doubt the tamron is a better lens than the IS kit version - but maybe not £150 better.
Canon has 2 good consumer lenses now, the 18-55 IS & the 55-250 IS - which cover a good range for most things an amateur would shoot.
You should be able to pick up both lenses for about £250 (£100 & £150 each - £240 for both on camerabox).
Im a bit pissed off I had to spend my money on car insurance - I was so close to ordering the tokina (

btw - have you seen the prices on flektagon's these days... £150 on ebay, im tempted to sell mine.