Is this nikon lens better than my old one?

So basicazlly, i went into a shop wanting an upgrade on my lens for my Nikon d5000 (I have the standard stock lens). My budget - 200 pounds.

From what i can remember, he pointed out the 18 - 70 mm nikon AF-S lens offers better optics and image quality than my stock lens.

He also pointed out a sigma lens, which he said was even better, but only if you were to obswerve the image to a huuge extent.

I just want to know, is the 18 - 70 mm the best option? Any examples?

Also, any other optons you guys could recommend? Looking for sharpness, auto focus is not an issue for me, possibly some kind of zoom, but i could probably go without if need be.

The best replacement lens for your 18-55mm kit lens is either the Sigma 17-50mm f/2.8, or the Nikon 17-55mm f/2.8. Both of these lenses are tack sharp and faster so that you can gain up to 2 stops in low light capability. Unfortunately, these lenses are a bit more expensive than your budget.

http://www.amazon.com/...003A6NU3U/

the 18-70mm is not a currently produced Nikon lens. They did make one a few years ago as a kit lens for the Nikon D70.So any 18-70mm you find today is going to be a used lens. It's not a bad lens, but it is not going to be as good as either of the lenses I recommended above.

And it is not worth spending the kind of money you are looking at spending as you are not going to realize that much improvement.

My advice, keep the 18-55mm you have and save up until you can buy the Sigma 17-50mm f/2.8.

I have owned the Nikon 18-55mm, 18-70mm, 18-105mm, 18-200mm, and the Sigma 17-50mm. The Sigma is the best of all of these lenses in the sense of sharpness and low light capability.

Better only in terms of slightly longer reach and slightly brighter at the long end.
I suggest you identify which end of the 18-55 you wish would reach further and get a lens to address that. 55-200 maybe? If its quality you want then think about a 35mm f1.8 prime.
The page in the link will help you a lot. Look for DX lenses and make sure they are fully compatible or you could end up with only manual focus and metering… That's fine if you are prepared to do it to use a special lens, not for regular use.
http://lenshero.com/lenses/lens-by-nikon

If you are not bothered about autofocus, perhaps look at some of the classic Nikkors. Non zooms will have better quality. They go cheap. You may have to use manual exposure I'm not sure about metering on the D7000, but you can get a programmable chip - the dandelion for about £20 I have a couple and it makes using old lenses easy.

A better option would be to save for the 16-85mm VR lens. The 18-70mm is not VR so doesn't have vibration reduction technology. The 16-85mm would give you a much sharper lens, more range at both ends and VR.