over wintering

Is what I use, It's the best anti-corrosion  product I've ever tried.

http://www.acf-50.co.uk/acf-50.htm

The construction of your storage area is important. It seems shipping containers and prefab concreate buildings with a tin roof in my experience are the worst. Also the water table being on the high side can mean dampness coming in from below.

I have found (In my experience) and where I am, is brick (Absorbent) and a fiberglass roof, generally watertight and thermal. Sound wooden buildings seem to work well too.

Apart from the other comments I would suggest a small dehumidifier to be turned on when the alloy shows dampness and putting a dry cloth up the silencer(s) to help prevent internal corrosion.

Finally, don't forget ventilation. Opening the garage door on a dry windy day for an hour should dry everything out on its own. But that sounds like a good day for a ride, even better.

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And always cover.  It massively reduces condensation.  Blankets, sheets...might also need plastic over it if the roof drips.  Also protect from those white spots of spider poo!

I have found that putting a cover on a bike provides the perfect habitat for mice who will happily make homes in the seat foam and nibble the wiring.

My shed had a tin roof so I lined it with wood which helps. A dehumidifier can help too but does not work in cold weather. 

Cover the bike in a cotton sheet and put a 60W bulb underneath, put this on a timer and/or thermostat to keep the cost down.

As previously mentioned a dehumidifier will remove dampness from the building.  But the building does need to be airtight otherwise you will be trying to dehumidify the outside air.

... my garage is brick built witha concrete floor and has an (uninsulated) timber and felt roof. I don't seem to get any condensation at all. I'm not keen on covers as they can get damp and foster rust etc.

Of course I never put snake oil in my petrol either and my bikes start first kick after weeks or months idleness.

Jammed against the kitchen cupboards may seem confrontational, but it's ever-so damned stylish. Second only to leaving the bike parked leaning against the bar at closing time.

I can only vouch for the fact that central heating pipes under the floor of an integral garage are a wonderful thing.

The best way to avoid condensation during the colder months is to ride your motorcycle frequently. If that is not practical I would suggest that you remove the cupboards and bring the machine into your house. It will be infinitely more interesting than 99% of the programmes on an ordinary television.