I take a different view. For a lot of candidates that I've interviewed in recent years, they made the decision to move to London, and _then_ decided to apply to us. Some of the best engineers that I've worked with have joined that way, and many of them stuck around for a long time. Of course the candidate should show an interest in the company. But frankly, if you're an employer in a place that people want to move to, that's something that you should be taking advantage of, not complaining when the candidate is honest about it.