Issues have been found with the wing stays:

The rear ones are not high enough to clear the tyre The front and rear ones rub against the wheel (MEV suggest using hub centric spaces 25mm bit rubbish really) and the rear ones apparently now created using new process Bending the wing stays to stop the rubbing against the wheel is likely to crack any powder coating if already applied Some have been offered replacement wing stays originally free of charge but now not much less than retail (bit rubbish really should fit to start or be FOC)

Bending the wing stay to stop rubbing

If you decide to get spacers go for Hub centric spacers, it's probably not a good idea to use the ones without the lip

If you don't want to buy another set of stays you can raise the rear ones by packing one end with washers and making the hole elongated at the other end

The front stay should be packed with some washers (there are some on the seat belts that could be re-purposed) as there is a gap between the hub and the stay. There is also a part of the hub that could be ground down to get a flush finish.

This was I believe from the first Mk3 to be IVAed, put together by a garage

This approach requires no welding, a tube is held on with a grub screw to the wing stay and the tube is glued to the mudguard using either Tiger Seal or Puraflex 40 PU Sealant & Adhesive