After watching several clips online, and reported increase in burglaries in Yorkshire, (particularly bad in West Yorkshire) using both snap\bump, I decide to install them. I've replaced both external doors with anti snap\bump locks. They are not cheap especially if you require spare keys cut. But the simple way the standard door locks can be defeated, its worth it for the piece of mind.
Do a search in Google for "anti snap and bump locks", the first link Handlestore, it gives details of what they are, how to replace the standard locks and how to measure up if you decide to purchase some. There are other sites online which show you how to do it.
They were easy to measure up and replace, they only issue I find is its sometimes a bit fiddly putting the key in to the lock as the ones I purchased have a straight edge on the end of the key, compared to standard keys.