Domain Name Query

[satnam]

Recently I found a niche which is good and pretty much untouched. But the problem is there may be not plenty of sites present in the niche but the domains name are pretty much all taken (no thanks to the related niche). So, what I getting now is 'mydomain-name.com', 'mydomain.name.com' & 'my-domain.co.uk'

I am confused here which one to choose!!!