I use plastic drawers and seperate my collection. However I would go with a suitcase, it can be small with a lock. It doesn't look very interesting either.
I got three nice boxes (small medium and large) and they are on top of my wardrobe x
Sorry was supposed to say they are from wikinsons, they were about £15 for them all x
I have a lockble draw, but have yet to find some more secure storage for the overflow and larger toys so they are in the bottom of a cupboard.