Why not get a folding panel and just connect up to the battery, I have a 150w panel and does very well and keeps my 110amp Numax battery charged up, so far 15 nights inc. TV usage. Gives out 8amps in full sun and a boost charge of 14.4v if needed. Charge controller is on the back of the panel, IP66 water proof.
Probably the best leisure batteries are the lithium ion or Lipo, although the Lipo are heavier than the lithium ion, but easier to manage.
Of course both of the above are far lighter than there lead acid equivalents and will also give at least double the service life of lead acid if not more.
Maybe if I had a caravan I would be looking at running a 48v system into an inverter to give full on mains 240v ac.
With a decent solar panel arrangement going of grid for a number of days would be quite doable with such a set up.
Lithium ion battery prices continue to come down, as the density increases.
Although the old technology and short service life of lead acid batteries along with being very heavy, makes them cheap as chips in comparison.
We have a solar panel prefitted to the roof of our caravan but if we are off the grid for long we supplement that with a set of folding panels like Octava4x4's.
No experience of fitting them, but I personally would get an "expert" to do it (if it involves drilling holes in the caravan roof!)
Our battery is a 110amp one from Halfords. I bought it from them for convenience; I hadn't realised my old one wasn't up to the job until we were just about to go away. Halford's was convenient and quite cheap (there was a deal on). That was 4 year's ago and (touch wood) the battery has been fine since. Powers our motor mover, runs the 12v circuit (lights, flush etc) and only really gets topped up by the fixed solar panel - I haven't had to recharge it off the van since we've had it.
We have a 60w folding one now, I find it a small pain when putting the caravan into storage and we go to a lot of festivals and I'm worried a larger panel would be stolen.
We'd only ever need it for 6 nights max and we would only really run our phones, iPad, the lights, mover and water pump. Think that's it? Maybe my current set up would be ok?
There are plenty of options on eBay for full kits. I would recommend at least 100w panel that comes with mountings for the 4 corners and 2 side supports, to give the maximum adhesion area on the roof. The kits come with the correct type of multifilament wiring, and the correct solar waterproof connectors. No need to hash it up with automotive stuff.
I'm pretty handy around the van, but I had the bonding done professionally. Getting it wrong and having the thing detach at motorway speeds was not a risk I wanted to take.