Simple solution Aileron. Go to local hardware store and buy appropriate lengths of hardened chain and locks.
When you arrive home and find your tie downs and all other taken by visiting CPL hour builders/ toolish charter pilots
1 Put chains and locks to appropriate use.
2 Attach phone number to chains.
3 Make sure you take your time getting back out to the airport to unlock said chains once you receive phone call.
4 Word gets around soon enough and TADA, unmolested parking space, tie downs and chocks.
5 Call their CFI/CP after they're airborne.
j3