The quickest route from the UK is via Brittany Ferries to St Malo. Good autoroutes take you down past Bordeaux and only the last hour is on secondary roads.
There are regular flights to Toulouse and Pau, Both British Airways and Easyjet have daily flights to Toulouse from most major British cities.
There is a good rail network with reasonably regular trains from Toulouse to Auch. As well as the TGV services via Eurostar, there is also the facility to put your car on the train from Paris to Toulouse.