I personally don't see why people stock up on things before they get here. Once you're living here, you'll be earning pounds and spending pounds. Thinking about how much things cost in dollars will drive you CRAZY! Plus, in most cases, the exact same products are available here and if not, you can usually find a reasonable substitution.
I always stocked up because I came on a fiance visa and wasn't going to be earning pounds for a while. Then, I got married in August 2005, didn't get spouse visa until Nov. 2005, and didn't get a job until April 2006!

So, I am sooooo glad I stocked up, because I kept spending dollars.
But now that I've got a full time job, I won't need to stock up anymore

I think it's a good idea to stock up at first. If you're in my situation, where you donn't earn money for ages (I didn't have a job until I've been in the UK for neary a year), it's a great idea to stock up. But once you have a job, I agree, there's no need to go home and stock up like your favorite things are running out!
Anyway Jen, I see that you're coming over to the Glasgow area really really soon! Good luck with the move and tell me how you get on.