Oh yes...rereading my last post, I see I was a bit vague

. Sorry...what I meant was upgrading to a different sort of lens. Not planning to upgrade the body any time soon.
I have a feeling you may be right about the Cannon. There's actually nothing technical to it..ultra responsive, and I just like the build and feel better. It's more solid- strikes me as being the business for not a huge amount more money.
How helpful do you think Nikon's guide mode would be?
The 550D is almost exactly the same price as the 600
second hand, so may as well go for the 600. I can get a used 600D and Cannon 18-135 for £539: 100 quid saving on buying new.
Do you think that would be a good choice? Equally as good as the 18-105 Nikon?
Is buying used worth the saving? Or shall I just blow my budget and buy new...

If I can sell nice crisp pictures with my articles, it should pay for itself pretty quickly.
Thank you very much again...