LAX-LHR is £600 each way to upgrade from WTP to Club. But when I did it, they told me (even though i faxed in all the details and receipts) that it was not eligible for miles hence why it was cheaper... they will give you a nice letter on board saying something along the lines of "thankyou for upgrading on board today. Maybe next time you won't be such a cheapskate and buy a ticket in Club so you can also use the lounge before departure..."