Lens upgrade (Canon)

[Mark]

Given the upcoming hols, I'm considering options regarding my 18-55 kit lens and whether it's worth looking at an upgrade. Given my (lack of) serious camera use, I'm reluctant to throw masses of money at the problem however.

My local camera shop suggested the EF-S 17-85 F/4.0-5.6, at £300-ish, which satisfies my needs (mainly giving me a little more wide angle and closing the 55-70 'hole'). I'm not sure what the IQ is like on this lens.

However, I'm rather liking the reviews of the new 15-85. I'd be prepared to hire one (£100), or maybe even buy one out there, use it, bring it home, and then decide which one to sell (obviously I don't need both).

Or of course I could just take the 18-55 and be done with it.

PS - I did consider hiring a 100-400 to get 'that' shot - but it's far from certain I'll pull it iff, and I've spent enough on that particular dream already.