If no cellar or wine cabinet, best place for storage is actually somewhere the temperature/humidity won't fluctuate too much over time. Garages tend to drop very cold overnight / in winter, so aren't best for long term storage. But I guess it depends on how long you "keep" your wine before drinking...now there's an idea for a thread!
I am getting married this summer (July), at my parents, and they have started buying wines for the occasion. They probably have about 50 bottles in the garden room, and do not have a cellar. They still have a further 150 bottles to buy. Should I get them moved. My in-laws have a cellar?