Changelly have finally been in touch and offered to either refund the transaction or exchange it at the current rate which is actually higher now. Absolutely can't complain about that, hopefully they'll be upgrading systems to handle this kind of demand when it happens next. Hadn't considered them to be trying a scam as used before without any issues whatsoever - just get's a bit stressfull when you're funds are suddenly locked up and there's nothing you can do about it.
I completely agree. I was not too affected by the downtime of both exchanges because I did not have that much Bitcoin Cash left to begin with, but because the first transaction I tried through ShapeShift took so long and eventually got stuck in limbo, I decided to give Changelly a try instead for the rest. When I noticed that they weren't responsive either I assumed it must have been an issue with the network; or in this case, the mempool being completely saturated. At the end of the day, my few trades on ShapeShift went through, so there is nothing I can really complain about.