That's not a garden lock, if such a thing exists, it the keep for a latch.
Point taken, it is just a plate latch installed on a door which happens to be serving the entry to a garden hence quite simplistically phrased it as such, one of the reasons for opening this thread to begin with is because I didn't know how its called but now that I know I can search for it.
Why replace it?
Because the latch is broken (not visible on the picture but it is).
Anyway I think I found what I'm looking for: http://www.ebay.co.uk/itm/232141869...49&var=531344115888&ssPageName=STRK:MEBIDX:IT
Anyway I think I found what I'm looking for: http://www.ebay.co.uk/itm/232141869...49&var=531344115888&ssPageName=STRK:MEBIDX:IT