soon to be new mac user. (hopefully)

Thanks for this thread-- i think its a great thread too,.

I have never used a Mac of any discription and have no idea what to expect.
So any info available on this site is much appreciated.

I was think of buying from Apple USA site as it would appear to considerably cheaper than buying in the UK- approx £400.
As I'm in the UK I was wondering if i purchased a Imac 21.5 direct from the US- would it be usable/compatable in the UK ( without any modifications.add-ons etc)
Would they accept an order from the UK being as they have apple shops in the UK.
Any advice gratefully received.