Last year I part exchanged our caravan, the one that we were getting rid of was under 2 years old, BUT I managed to melt the GRP side panel (don't ask......), an area around 8" x 2".  The dealer had it repaired and it cost me £450.  The repair was invisible, even in direct sunlight.  I restore classic cars and can spot a repair a mile away, but this really was good!
The downside to any caravan repair is that it will be done using paint, whereas the original factory finish will be a different process so there is a chance that the repair will weather differently over time and become visible later.  I always tell people not to polish any repairs after they're done with any too aggressive/abrasive.