SJPP to Paris

Easyjet has a flight from Biarritz into Paris CDG and that would be the fastest way to get to the airport.

You would need to take the train from SJPdP to Bayonne and then a bus to Biarritz airport. The last time I flew from Biarritz, I needed to stay in a hotel close to the airport as the train/bus combo from Saint-Jean did not work for an early flight.

I've been caught in the past and am now very wary of trying to meet connections for the trip home. My preferred option is to arrive (say in Paris or London) at least one day before my departure for home. That way there is a little leeway for adverse weather conditions or, in the case of trains, a strike.

Good advice Julie ,
I too tend to be over cautious, when travelling on an important or expensive trip I always leave enough time for alternate transport options. A night or 2 in Paris is preferable to missing that main flight which often is a discounted fare with no flexible options ie use it or lose it a short notice replacement airfare can be many times more in price.