gret idea to take advantage of the high BP, and get some shopping done but dont forget the following;

most gadgets and electronics have universal voltage (since its 110V in US, n 220v in UK) but u need to double check;

also the Hz; i dont know the technical aspects but i do know that for tv's for example it makes a huge diff (canada tv's are/were 50Hz and France was 60Hz

usually when u have cargo shipped same time as your flight, there is a sizable reduction in price (last time i shipped from montreal to abidjan i saved over 50% of the quoted ship only price. this was with AF)

good luck and happy shopping!!

PS: u will of course need to get an adapter for your gadgets ie the targus travel adapters sold in planes