I booked J out, F back, to CPT on a Ax 2-4-1 at the weekend and charges came to just under £225, sure I paid the £15x2 supplement, but I had a really helpful agent and we juggled the dates to make them work when one of my first choice legs came up with only one award seat available.
An extra £30 for that sort of ticket.. don't cause me a problem. ^