You can stay overnight free of charge on Port Solent. It is about 10 minutes from the terminal, or you can park on the BF car park after about 8.30pm.
Once you get into Santander, it is 3 hrs to Haro, 3.5 to Navarette or about 4.5 to Zaragoza all motorway. Bear in mind though you are going through some high ground in Rioja and down to Zaragoza & even in April you may encounter snow & cold nights-definitely in January. If you stay overnight in Haro, make sure you have some food with you as most restaurants don't open until about 8pm at earliest there!
Have fun
Mike