Identify this lock?

[chipperhead]

I need to replace the lock in the porch door but I'm struggling to find a replacement.
As you can see from the picture it's not flat but shaped to the profile of the door. Is there a specific name for this type of lock as I can't seem to find one?

Thanks

 

[chipperhead]

http://www.handles4doors.co.uk/door...ice_locks/easi_t_2_lever_rebated_sashlock.htm