Tony,
For the repair, I can recommend a 3/1 mix of my mother inlaws mashed spuds & broccoli. I used this with great success repairing a cracked block six years ago. If you replace the broccoli for crush and run its good for paving too.
Failing that, can you lay your hands on Dennis Neilsons bath matt? It may whiff a little but it has excellent waterproofing & pest control properties. HEVAC, will no longer present any issues for you as you'll be the only fooker in the car!
Kind regards,
Foultrousers