I had one like that and the bike was fine. If you leave your bike in it over the winter though get one of these to keep the battery topped up as it wont have any power sockets.
http://www.maplin.co.uk/solar-powere...-charger-98358
The only problem I had was with my insurance company. The insurance company wouldn't let me say I kept the bike there because it didn't have it's own postcode so in the end I had to just say I kept it as home under a cover, only added a few quid to the premium anyway.