Estepona is usually very nice in March. It is still a bit early so the weather cannot be guaranteed. I have been there for the last 12 years in March and I cannot complain. I also drive there. I have not found it neccessary to use the French toll roads as I don't consider the time/cost factor to be worth it. There are a number of roadside hotels in France of varying standards. i tend not to use Formule1 as they dont have a private shower. Anything I can help ith please ask.

what will weather conditions be like, through France, it will be approx 18th March. We did it last year but that was in May and we went to Santa Pola, not as far as Estepons but thought with it being a couple of months earlier we needed to go further south. thanks for your reply
After wind and rain throughout Fance, we were snowed in at Burgos ( northern Spain ) but when we arrived at Estepona ( it was the Marina arear, had a great couple of weeks , then the heavens opened approx 3-4 days then nice again, Still plenty of Bars ( Some Where Else ) name of bar just under our apartment, the owners were great, fun people. overall we had a Fab time,

I do not know the conditions in france at that time of year as I always come earlier and go home later. As a matter of fact I have just driven through france 3 days ago and the weather was fair with a bit of fog.