just changed the tyres.
the rears were worse than I originally thought and did have some significant inner wall wear that was not easily visible clearly until the tyre was removed. It is worth checking for this carefully as it is really difficult to see on the car unless its on a ramp etc.
whilst there was still some tread on the fronts, there was some outer shoulder wear on one tyre so in the end I changed all 4 for 453s.
E91 330d Touring M Sport Auto 2006
225M 19" MV4 + Falken 453
M3 270M 18" rims + Vred Wintrac Extremes