I believe that is about right on these old 2 strokes using 30 grade oil. If using 2 stroke oil it can usually be relaxed to about 24:1, although I always err on the oily side especially as some old Villiers have plain bearings don’t use crank seals and rely on a oily mix to stop crank-case leakage.
I use Villiers Classic 2 stroke oil at about 20:1 in my ATCO, and yes, it does smoke a bit but, at least it won’t seize up !