Series 2 subframe fits S1 coupe, not sure about saloon/HPE though.
I've had a look at the tech data and there is a dimension on the bodywork checking data for the 'front subframe rear mounting bores' on series AB distance to centre line is given as 220 +/- 0.5 but on series CB/BC it says 251.7 +/-0.5 there also seems to be a difference as to where the subframe 'dowel holes' are positioned. However the subframe data only shows the earlier dimensions (I'll have to measure the subframe mounts in the garage) but maybe this info was never updated?