I haven't used Madam Sew, but I have bought various sewing machine feet from China.
They were OK on my Pfaff, but the Singer didn't like them much, and they kept hitting the needle plate.
Also, the ones I bought had to be used with an adapter, which is why I don't use them more. In order to use the adapter, you have to remove the shank. Too much of a Pfaff for me.
Far easier to buy the feet you need as and when you need them. Also, it may be of interest to know that Helen Howes sells lots of SM feet on her website, and if you have an older machine, you may find what you need on there.
Jessie