GARAGE EN BLOC.
Or garage at the end of the road if you don't speak estate agent!
This option requires a little more thought and determination to make secure. Being at the end of the road it is very tricky to keep an eye on it all the time and for some reason garages like these seem to have rooves that are made from corrugated tissue paper. So the roof is the first line of attack. If you have one of these rooves, reinforce it with a sheet of steel weld mesh bolted to the rafters. It's pretty light and can be bought cheaply from your local steel merchants. Cover this with tarpauling so that if and when thieving scum come calling and smash the corrugated stuff in, they won't see their prize and it will stop the bike getting wet when it rains.
The walls of these garages are usually brick but if they are not then use the same technique as the roof.
Now it's time to do something about that poxy bit of metal that the council seems to think is a door. Fitting an anti ramming post or door stop does really give the game away as to what garage has got the good stuff in so paint it the same colour as the door or instead fit internal deadlocks that operate through discrete holes in the door.
If you have 2 separate doors that open from the centre then ensure that the screws that hold the hinges are only accesible from the inside of the garage and that all the wooden panels are well screwed onto the doors. If you have the inclination bolt a steel sheet to the inside of the doors and make sure that any locks are bolted through it. Ensure that the bolts on the static door are good and secure top and bottom and consider fitting another pair at the hinge end so even if the hinges are removed the door will stay. On the moving door ensure that there are at least 2 padlocks each at 2/3 and 1/3 height.
Alarms are a good idea but during the winter if you don't use your bike regularly you will get very good at bump starting it from a flat battery. If you have power in there then use a battery maintainer like an Optimate to keep the bikes battery fully charged. You could even fit a pager to the alarm system that will alert you in the house (don't pay £250 quid for one I can get good uns for £100). A shed alarm is also a good thing but only if there will be someone nearby to hear it.
Then the final and possibly the most important piece of kit will be the huge padlock and chain secured by a humongous ground anchor