It was in one of those gadget catalogues that falls out of the telegraph/mail/etc.
A great big (breathable?) sack that could hold an entire bike with a drawstring closure on top? Just wheel the whole bike in, close the drawstring, carry bike into house.
They were about £25
Need one to store the bike at the girlfriends house rather than having to faffaround with the garrage which is the far side of the car park and in full view of the local scrotes.
There are some on Ebay IIRC. Otherwise you could try modifying a survival bag.
King size Matress bag from a local bed store. Free.
materess bag might be the winner, the original one I saw was like the roots one, but covered the whole bike, cant imagine I'd be in the good books if mud started flaking off the saddle/bars!
Wiggle doing clear plastic bike bags for about £7.00.