ive tried cliff jumping at an old quarry myself about 35ft high but it wasnt the best as there was always dead cows that had fell off the cliffs or "pushed off" and burnt out cars were always in the water as it was a haunt for joyriders pushing there stolen cars off the cliff when they were finished with the poor buggers cars,also tried jumping onto artics roofs which would pass under a railway bridge"they would only be doing around 20mph as there was traffic lights just ahead of the bridge!!
i watched too many james bond films i think lol