hi Mathy, never use W4 to lubricate any lock, the reason why is because it's a liquid, so dust will stick to the lock, then cloak it up, only use graphite powder.
You can buy a small amount, it's cheap but it will also cover your hands when you use it, but wash off.
Rubber shovel, it's a classic isn't.
Great point Mathy about mentioning the 'mesh' it absolutely works, I've used it before, another way is to get a piece of (gyprock) plasterboard, you can pick some up from a building site will give you some FREE.
Next I'll tell you another way, and what I say makes it seem as though it will a long time, but no it won't, my description maybe long but when you get used to doing it this way, it takes only a couple of minutes.
Buy a small bag of cornice adhesive, Mathy will show you where it is, it has to be cornice, because it 'goes off quickly', in other words goes hard quicker.
Cut a piece that will go through the hole then put in the hole in the middle of it and then put a string through it and tie it to a nail or something similar.
Mix up a small amount of cornice adhesive and put on a piece of plaster, then pull the plaster towards you with the string, either hold it or tie it to something that won't move.
Leave it there for a couple of minutes, maybe 10 minutes or so, or even longer(long description isn't it, but I assure you it's quick), cut string and then cut another piece that will fit into hole, then put some cornice only a small amount and put into hole, then you can finish off.
Quite agree Mathy for a quick fix use the mesh, but if you're short of finances visit a building site, ask and they will give you everything.
Boy, well the mesh sounds to be much quicker, but if you're adventurous then have a go. Geoff.