Sad, but true.
Funny thing is that I actually have a small circular saw with a blade made for wood, but of course, I cannot find the blade for cutting plastic here. Two choices - wood or ceramics blades - not one suitable for a thicker plastic. So, hand sawing it is. You can achieve some better results with sandpaper and - lot's of patience and time.
Maybe it's time to get a mitre saw (I was looking for them, found 'em, and - guess what - no other kinds of blades but for wood
)
Hehe, time will tell...Lot's of time, I suppose...
Cheers!