Getting to Cahors by Public Transport
There is a bus service between Blagnac (Toulouse) Airport and Toulouse Bus
Station (Gare Routière), which is next door to the
main railway station, Toulouse Matabiau. The bus runs every 20
minutes and the trip takes 20 to 45 minutes, depending on traffic and/or
road works). The fare is 5 euros, with a free transfer to the Metro or city buses.
The train between Toulouse and Cahors takes the main line to Paris;
the fare is about 20 euros. The taxi ride from the
station to any Cahors address should be under 10 euros. By the way,
there's an Avis office at Cahors Station.
Trains run from Paris (Gare d'Austerlitz) to Cahors, taking just over 5 hours. They are fast between Paris and Limoges, but run slower through the Massif Central. There is often a food trolley on board, but you might consider having a picnic if you have the time to shop inside the station beforehand - you won't be alone if you do. The cheapest way to travel between Gare d'Austerlitz and Charles de Gaulle Airport (Roissy) is via the RER blue line and the Metro: the most expensive is via taxi, about 50 euros. You can also take the Air France bus from Roissy to Gare de Lyon, which is a walk over the Seine to Gare d'Austerlitz. How about spending a day or two in Paris on the way? If you stay near Gare Montparnasse, consider taking the TGV to Montauban and a local train from there to Cahors.
Buses run several times a day between Cahors railway station and Fumel, to the West, and between Cahors station and Figeac, to the East. These are run by TER, a subsidiary of the French rail system: you can see their times on the SNCF site (they are listed in the train schedules, but the annotation "autocar" tells you that they are buses). There are also some independently run buses between Place de Gaulle and Lalbenque, Montcuq and Castelnau-Montratier, mostly timed to take children to and from school.
Brits may be interested in the weekly Eurolines coaches that run from Victoria to Cahors, changing at Tours. The trip takes about 18 hours.
There is no convenient public transport between Cahors and Rodez or Bergerac: a taxi between either airport and Cahors costs over 100 euros. RyanAir passengers without friends to pick them up need to rent a car.