I agree with Swiss Tony that in your case it was frankly too good a deal, I don't think BA were making much money out of you, given that they are running their services fairly full at the moment. So I am afraid that if BA loses your custom with this particular arrangement, then I don't think that's going to bother them too much.

Reading between the lines, you got your Avios from the WTP cash cost plus presumably a Chase card or some such, with a 2-4-1 helper too. So you were getting redemption space without being much of a revenue BA customer - and these hardcore BA customers were then struggling to find availability. So the scheme has been adjusted so that the Upgrade using Avios (as MFU is now called) deal is not as good as it was, the peak/off-peak component is now there to spread the load, and they have sharply increased the availability and its predictability. Swings and roundabouts to many customers, though I guess not in your case, and probably intentionally so.

You can reduce the cash component by flying Aer Lingus or Air Berlin, though the Avios component is higher and you won't get a UuA or 2-4-1 on them.

You also paradoxically reduce the UuA amount by travelling at peak periods, from 48k off peak to 40k peak (return fares). Presumably the cash component would potentially be higher though.