I've looked at the parts books. Series 2 Coupes and Sports were fitted with a 2-speed motor part 2278949. It was also used on the 2000 (820- flat-4) car. A different heater motor was used on the S2 saloon. Series 1 cars had different part numbers for their fan motors, 1.2 was 2229815, 1.3 2249270, 1.6 22676680. All part numbers later preceded by an 8. I don't about physical compatibility. I have a brand new 2278949 for the S2.
So I'd be careful about buying an S2 part for an S1 without checking with someone who knows. Maybe Neale Shepherd?
Hope this is of help
Paul Mayo