I bought SPDs and had to buy those reflectors separately so that I had reflectors (lbs ordered them in for me). Regardless of the legality or otherwise of not riding with reflectors, I prefer to have them on - after looking at other riders in dusk or at night I think they are worth having, they add to visibility and the movement attracts the eye of drivers too. These ones are good as the weight of them keeps them hanging down, so you are always able to clip in as your pedal is always the right way up. I have ridden short distance with the platform, agree with Mulger that it's not much chop but you can go for a spin to the shops without your mountain bike shoes on.
I bought my bike without wheel reflectors, which are also required at night. Tried for ages to buy them, not for sale anywhere. Eventually a lbs just unscrewed some from a shop floor bike and gave them to me, said everyone removes them anyway. My concern was always commuting at dusk or in the dark on a bike that didn't meet the code, gives a driver who hits you a potential way to reduce their own culpability and maybe even avoid responsibility completely (of course, it would never be my fault
) Must admit to riding most of this winter without them, not such a big deal with days getting longer. Would be interested to know if anyone else uses them.