I shall have a go with the original steel wheel bolts from my blue Bis on the alloys and see whether it will fit. Hopefully, they will do. If they do fit, I will be short three bolts. Three wheels from my blue Bis have only three bolts on them.
The M12x1.25 bolts from ebay come in a variety of lengths. I shall measure the thread length of the original steel wheel bolts and buy new a new set from ebay, that is, if the bolts are suitable for the alloys.