Finally bought tyres through Asda. They have deal with Halfords fitting centres and gave a great discount (BMW £!!! **: National Tyres £722: Kwik Fit £650: Asda £543 fitted and balanced). Fitter questioned that all tyres on car were 205/50R 17 and I had ordered 2x 205's and 2x 225/45R 17. He wouldn't fit till I had confirmed this OK - (he thought only high end spec models had the wider tyres on rear). Phoned BMW dealer and they confirmed that 225/45R is preferred rear tyre and that they didn't specify tyres on original, new car. That was how it was sent to them from BMW! So, driving experience is same as but if anything I'd say car turns in better. (That may be just because I've got new tyres and I know they are different at rear). And yes, they were round - all round!! lol