The only ways I know of getting reduced prices are using BAA Worldpoints for half-price travel (50 points) or upgrade to first (100 points) [can't do both at the same time though]. But it may be more worthwhile using your Worldpoints for BMI DC miles instead, but I've not worked it out).
I think if you have a BAA Worldpoints Credit Card you can get some sort of discount/upgrade without using any points though.