A bubble is a more complex phenomenon than large price increases. A bubble is inflated by speculation that isn't rooted in anything except the rising price.

If rich foreigners are buying property to summer in because they like the weather, then not a bubble. If rich foreigners are buying property because the property has gained X% in price every year for the last ten years but they don't know anything about the specifics of the local real estate market, then more likely a bubble.

You also can't say something is a bubble until after it pops.