There are a reasonable amount of wheels open to the 4x108 PCD the sunbeams use, as its comon to porsche 924, saab 900 (early models) ford capri, escort, mustang II. However you have to watch the offsets as they are often not ideal from sunbeams.
While the superlite/minilite/panasport typerims are popular due to availablility/size/offset and the fact they are period for the car they do get a bit comon. There are good alternatives from VTO, PS wheels, Image wheels and period options from Sunbeam Specialties of the LAT 70s.
You then have period wheels you can find on ebay etc..dunlop D1's, cosmics, revolution revolites, Eneki etc.. but they are generally 13" x 6
Do you want 13, 14 o 15" wheels? Period or modern looking?
People have gone to 5 stud, and it would open up choice.. but depends what choice you want.