BA is trying something new again with a mileage subscription. You can subscribe to receive a set number of miles each month, and the price is cheaper than buying miles outright. There is also an annual option: subscribe for 12 months and get 2 extra months. The cheapest option is 200,000 BA miles per year for just £1,789, which works out to only 0.9 c/p based on the exchange rate. If you switch the display to U.S. dollars, it shows $3,069, or 1.5345 c/p. You can try changing your account address to the UK and see whether you can pay in GBP.
That said, unless you have a specific need, I still would not recommend subscribing. BA miles can be transferred from AMEX and Chase, so if you already have a large stash of points, it probably does not make sense to lock yourself into earning with just one program.