I've had a recent problem with my S reg Combo starter motor, a search online didn't find any usefull answers, just the usual "take it to a garage" stuff as above.
I'm a practical type person so took my starter motor off anyway, to help anyone else who finds this thread while searching like I did, here's how I removed the starter.
I'm sure anyone trying this job knows about safety and having the vehicle parked on a flat level surface, doesn't rely on just a jack to hold up the vehicle while working on it.... blah blah blah!!!
First, remove the battery, taking off the negative connection first.
Remove the 4 bolts holding the battery tray in place (13mm socket)
Underneath the car, at the back of the engine, remove the pozi drive screw holding the LT lead to the back of the solenoid, remove the top nut connecting the thick cable to the back of solenoid (I found this easier to do once the starter was hanging loose)
Back above the engine, loosen the 19mm bolt that holds the starter motor to the gearbox (it's a tight squeeze to get access to it)
Then back underneath, loosen the bottom starter motor bolt (14mm)
Back above, remove the 19mm bolt, underneath again and while supporting the starter, remove the 14mm bolt.
The starter can then be jiggled about to remove it completely.
Taking it off, cleaning all the terminals and re-fitting it took me 2 hours.
Pyewacket, January 2009