Winter 2013/4 in Spain

He who must be obeyed is once again saying he can't stand another winter in the Uk! (I don't know why lol). We've talked about it before but get cold feet! We have a caravan and will be taking our dog with us who is used to caravanning and travelling to and from France.

A few questions:

We'll probably go for 7-8 weeks. Any suggestions on what would be the best time to choose.

Long ferry trip or short? Pros and cons!

Is it necessary to book a site for what will be our main 'places of residence'?

We aren't really 'rally' people but would like to be on a site where there are at least a few Brits. Before now we've travelled round France and hardly spoken to anyone who was a native English speaker and I don't fancy doing the same for a more extended period of time. Any suggestions for areas/sites would be appreciated.

Thanks in advance!

Chris