If you ever attempt to fit your own locks as part of a DIY project, it is always important that the locks you fit to external doors are British Standard. It is often tempting to opt for a cheaper lock and with many DIY stores stocking internal 2 or 3 lever locks at good prices, it is easy get confused. The 2 or 3 lever locks are meant for internal doors and are seen as medium security. Many insurance companies will not see this as adequate security and this could harm any claims made.
So ensure any locks you buy for yourself are 5 lever mortice locks and not meant for bathroom use. Better still, call a Locksmith!