This has been talked about in a previous thread but no real details were given on how to perform the discount so I figured I'd submit it as a deal (however it'll most likely end up freezing).
Currently BF3 Premium for PC is £39.99 from the origin store: http://store.origin.com/store/eaemea/en_GB/DisplayProductDetailsPage/ThemeID.850300/productID.249982800
However by changing the origin store from UK or US to India or Brazil you can get a heavy discount for the same downloadable item. I purchased it for Rs 1,499 (that's Indian Rupees): http://i.imgur.com/PfcF8.jpg which works out to £17.49: http://i.imgur.com/3TYVY.jpg
The content is in English and there are no downloads needed as BF3 is automatically updated regardless of if you have a certain expansion or not. So as far as I can tell it's pretty risk free.
Now onto how you change the origin store location. The stores location is based off IP so you need to have a proxy or VPN to get there. Within 2 minutes of looking online I found a good list of Indian proxies: http://spys.ru/free-proxy-list/IN/
Not sure on other browsers, but in firefox go Tools -> Options -> Advanced -> Network -> Connection Settings. When there enter one of the proxy IPs like this: http://i.imgur.com/VivYR.jpg . Head to www.store.origin.com (if the UK site loads delete any cookies you may have stored for origin). If the site fails to load try another proxy (some will be faster than others).
Once there add BF3 premium to your cart and head to checkout. When you're on the payment page, disable the proxy (i.e. in the Connection Settings choose 'No Proxy') and complete the checkout. After that's done you should receive an email 5-10 minutes later and you will be automatically upgraded to BF3 premium.
May seem a little tricky, but I just wanted to make sure I covered all the bases so that anyone can get the discount :). Just remember that this will be an overseas transaction so some credit/debit cards may have a £1 charge, but still works out far cheaper.