The cover sold by John Taylor is by far the best IMHO. I have used one on both my Mogs and even the Irish rain has never manager to get in!!!
Cheers!
That says something for JT covers!!

Mine is getting a bit tired now (the elastics have stretched and a seam is going) but it still keeps almost all the water out after 6 years - and for the first year it was on the car for much of a winter, so I'm in agreement with you Robbie!
Cheers,