I just wanted to say that I used a folding 13W solar panel to keep my leisure battery charged whilst staying at a festival for 1-week with my family. We used our solar charged battery for the 12v lights, water pump, and charging our phones / tablets. I was very pleased with this as I wasn't sure if a 13w panel would be suitable for the job. The battery charge indicator stayed in the green for the whole week (and it was quire overcast on some days).
I've always been a bit nervous of going for more than a night or two without electricity but I bought one of these solar panels recently (Maplin £63.99) to go away for 5 nights. As you experienced, indicator still on green at the end of the stay. Well pleased.
Yes - I was worried too, but the 13w panel was fine for the lights, pump, and phone charging. I've got a 75Ah battery. I've also started using a 4w panel to trickle charge my battery when my caravan is in storage - that keeps the battery topped up, even over the winter with battery still in its caravan compartment. I don't think a 13w panel would suffice for any heavier usage such as a TV. I'm pleased about it as I can now now go anywhere without having to worry about having an electric hook-up.
That's good to hear as sometimes you see people saying you need at least 28w or even more like 100w. Like you I've found that a 13w panel is fine for lights, pump, phones. Do you use your panel for similar things?