Just done a bit of checking around the UK, the Norvick type of oil control ring (the type with the backing spring) - the Ex DAF\British Leyland one are almost extinct in the UK, it seems impossible to get a full set of 4 from one source, eg Skytrade has 2 and no sight of any others in the near future.
If anybody knows different - then please let me know asap!
However, it seems that the slightly less efficiant H&S type rings are more readily available.