The appartment is quite close to the beach and inner city - the appartment per se was ok and the price was ok, but not very clean when we arrived. The check-in is unnecessarily time-consuming, towels and linen (who had dirt patches) cost extra, both is a no-go for us. Some household utensils that should be granted were not there (like toilet tissue, soap, garbage bags), so there was no big "welcome feeling".
So all in all, we had a good time in Biarritz and in the flat, but I would not recommend it.