Buying from the US

As a collector based in the UK, is it practical to buy coins out of the US? Is there anything I should be aware of as regards customs etc?

There might be import duty payable (5%) and VAT (20%).

Also the shipping costs are prohibitively expensive.

Also, you might pay some attention to the Exchange Rate.  

I'll often shy away from purchases if our Canadian Dollar is performing poorly versus the USD, Pound Sterling, and / or Euro.  I have stayed away from many US purchases since September but, just yesterday the USD dropped 7 cents (approaching a 5 year low).

I think it is not a simple answer.

I have occasionally shipped a coin to the UK in a first class letter, and charged the customer $1.50 for postage (I would need to charge a bit more now).  This can make sense for some situations.