this is a tester video for the hiplock d1000, yes it's £250, but i would say it's a lock that gives the highest chance of your bike being there when you get back.
there are other things to point out. for insurance purposes you need at least a Gold rated "sold secure" lock, usually available from £35, i do a few at my shop, various brands, if you have at least a Gold lock your insurance should pay out without question, if however you simply don't want to deal with that then stump up the cash for the hiplock d1000.
in this video, when you past all the silly attempts like hammer etc, he finally goes at it with a grinder. here's some things to point out. he did eventually get through it, it took 2 1/2 discs to get through only one side, because of the way the lock is you'd still need to get through the other side, that means he'd need 5 discs in total to get through the lock, also he had an electric plugged in grinder, not a crappy little portable thing with a only a small disc, i'd point out that most thieves won't carry 5 plus spare discs and even if they did the battery life at full power which you'd need will only last about 18 minutes and that is a long time to grinding at a lock without someone questioning you grinding a lock.
the d1000 is motorbike and bike rated sold secure diamond level