Funny you should mention this...
Had my MOT only a few days ago, and the guy said i had a small pin ***** hole in mine, cos it was spraying grease out, anyhoo..
When i got home I had a look, and it didn't have a hole, it was just that the o/s inner cv gaiter had moved, because they don't have any metal bands around the stopping them moving, like most other cars do.... Wierd
I'd have a look underneath if i were you, just to make sure it's not the same as what i had, in the end i cleaned what little grease up there was, and stuck a cable tie round the smaller end of the gaiter, to stop it moving again, so i'd check this if you can first before spending loads of money having them replaced, as it is a 'BIG' job especially to do the inner ones.
It seems madness to me that there isn't any thing to stop the inner CV gaiter shifting on the drive shafts and for grease to be able to get out... Just Crazy & poor design