I rent space in a barn for two of my cars. Landed in my lap as the owner was walking past one day and saw two Triumphs in the driveway, so popped in and asked if I was interested in renting some space..do check to see if work can be undertaken on site.
So, if situated in the country, look at farms and see if any have barn space.
Otherwise, small adverts in newsagent windows might throw something up.
As for building a garage, I would always consult the Local Authority Planning Officer to find out the local planning conditions. For example, the Borough Council that I live within charges approx £60 to let one know if a)Planning consent is required and B) if one sends over a sketch of the proposed garage and location within the property site, if there is anything one should be aware off.