You can arrive into Clermont Ferrand by aeroplane into Aulnat Airport.

You can hire a car from the airport or take a taxi ( 10 minutes or so ) into the city centre.

The problem at the moment is that it's really only domestic flights only, mostly by Airfrance it has to be said! You can fly KLM (owned by Airfrance now ) to Amsterdam and then pick up a connection to Clermont but it can prove expensive! However, excitingly, especially for those from the South of England, flights to Clermont Ferrand look set to commence three times weekly from April 2008! 

Alternatively, you can get the Eurostar to Paris and change stations to catch a connection to Clermont Ferrand which isn't a hassle and the journey is a pleasant one taking about 7/8 hours or so. Once in Clermont you can get a taxi to the centre, about 5 minutes or maybe the tram.

If driving, it's not a hassle driving into the city centre. Certainly not like London or Paris!

Bon Voyage!