Try sending the Dr on here a pm, he should be able to help or advise...
You're not going to like this, but £160 from Samsung themselves is actually quite a good price.
The glass (Digitizer/touch) and the LCD on these are bonded together, so most places will change both as one unit, this will ensure that you get a good fit and your phone works properly.
There are places that will say they can just do the glass, but it never looks quite right and if they break the LCD trying to separate them (which is more common than actually separating them) they'll charge you for that as well (with a "there was a fault with it" type excuse).
I know it's expensive but if you get Samsung to do it at least you'll keep your warranty intact.
Failing that, if it's not too bad and you can't see it, put a screen protector on to keep the little bits of glass out of your fingers, and put up with it for a while until the prices come down.