Recently spoke to a friend who has one fitted to his S2. He said the gearbox end is p'n'p. The selector itself sits a bit further back than the original one and can be left that way (he did), but ~1-2cm can be taken away from the selector rods if one wants the stick to sit exactly where it was. Then the plastic casing of the selector box is a bit wide to comfortably sit in the S1/S2 chassis tunnel and a little grinding was needed. The fixing to the body is different and can be done with the Puma's bracket or any other way one sees fit. The selector itself is quite cheep, cheeper than overhauling the old one. It's around 100e here at Fords, so around 60-70£ over there on the rainy island.