Assuming that you want the beach to have a good chance of some warm (or hot) sunshine, you need to be heading south.
For decent nightlife and good shopping, you need a large town or city.
So, putting those together, your only real option on the west coast would seem to be Biarritz (which is next to the Spanish border):
http://www.biarritz.fr/en/Website/site/en_tour ism.php
The French Riviera offers more choice. Nice would probably be top of most people's lists:
http://www.nicetourism.com/GB/som.html
(It's on the border with Monaco, so you could visit Monte Carlo. In the other direction, Cannes is only a short distance away).
Chris