we usually do rallies and I have to sometimes work on my laptop, so we use a generator, most people hate them but they are more acceptable on rallies as a good majority of the group use them (or they do with the ones we go with)
------------- -x- Diane -x-
May 13 - Cala Gogo, St Cyprien (didn't go, hubby too ill to travel)
May 14 Ranc Davaine
August 14 Les Sablons
August 13 - Camping Playa Brava, Pals
Might be worth tinkering with the power settings on your laptop to make what power you do have go a little further. On some laptops you can slow down the processor slightly and set hard drives and monitors to turn off after a short amount of time. That might help to extend the life of your power.
I'm not an expert, but would solar power be an option?
All you need is an adaptor which you plug straight into the 12v supply in your caravan. It has the 2 prong plug one end and a cigarette adaptor socket on the other end You then plug the lead from your laptop ino the cigarette adaptor and bob's your uncle.
I bought a Tevion notebook travel charger from Lidl with loads of adaptors for mobile phones, laptops and TomTom etc. It was about £15 and was before Christmas. I am sure Maplin or Currys will have a similar set up and then you follow Surfers directions.