Cleaning - birds

 I'd get a wet rag and leave it to soak the muck. Keep the rag moist by giving it a squirt with the hose. This should do the job of removal, but you might have a stain mark that needs polishing out with a good car polish.

I've used this method on my grp roof so I cannot see why it would not work on your rooflight.

Colin

We use Autoglym Caravan and Motorhome Cleaner followed by their Resin Polish on the bodywork and have always achieved  good results.

I use an extending handled brush (like this: https://www.ebay.co.uk/itm/310514013164?hash=item484c13d3ec:g:yVAAAOSw9jVhL1XZ) for cleaning the roof/skylights from a step ladder, it's good for cleaning the whole van.  Our skylight can also be cleaned from inside the van as it slides open wide enough.  I use regular car wash and wax and agree with the pre-soaking tip if it's heavy soiling.  I  bought a special polish for plastic windows (renovo from memory) and that works really well for small scratches, so I'm sure will resore the roof light if there is any stain and leaves it easier to clean/sheds water better once polished.

Have you tried any branded insect remover products?

On paintwork, bird poo can stain into the lacquer if left untreated too long, not sure how it affects perspex but worth a try.....

bird poo will go right through the paint if left long enough - that on my Cortina so obviously a while back 🙄  .... the speed depends on the time of year & what the birds have been eating. And as caravan paint isn't as hardy as car paint, it needs to come off sooner rather than later.