Ok everybody.
No more foccing about with wd40 or grease.
I remembered someone on here ages ago saying that the only thing for locks is graphite.oils end up attracting more dust and making the problem worse.
My front door lock was totally focced to the stage where it was an absolute struggle to get the key fully into the lock and my missus got locked out coz she is too puny.
Anyway a quick google to amazon gets me this little bundle of joy.
1 half second blast in the lock.....instantly fixed
.....not only is it fixed but it is without doubt the smoothest lock i have ever encountered.
Leave it 40 days for your wd40 to bugger off and get some of this in there.