I would say it is your responsibility, I think the building regs are for all new builds, I know there are plans that from next year all houses have to comply with certain regs but at present all 2nd hand have no such obligations. It is the same with the location/height of light switches, the size of DS WC, which now much be a certain dimention, but previously were a lot smaller, and it is not appropriate/possible for some older houses which do not comply with new regulations.
I would say if it is not toughened glass, it is part of your responsibility to install it. There are no penalties for living in a house that doesn't comply with building regs, but anyone building from new/extending may have to comply with the up to date regs.
I am not overally qualified in this field, but the above would be my opinion.