Hi' I use the 50/ 1.7 and 135/ 3.5 great lenses. The 50/ 2 is a good lens as mentioned,the only benefit really for the 1.4 is if you need the speed or like shooting wide open to get lots of bokeh. If you like wide the 28 and 35 f3.5 seem to be better as they are sharper in the corners. As to whether or not to keep the mx unless to your eye it's just to ugly to be seen with a good cla from a good tech would be more cost effective. Not sure who in the UK to recommend for that.