Is there an easy way to determine where your from e.g. viking, celtic, saxon etc?

I wouldn't trust any physical indications. As another poster mentioned, DNA is probably the only sure way. There are some known areas that make it more likely however. If your family happens to be from Ireland, Northern Europe, or parts of Russia, it's certainly more likely. Russia is even named for the vikings, ie the Rus. Celtic and Saxon is even harder to pin down than the vikings. If your family hails from anywhere from Spain up through Scotland, you can at least claim to be Gaelic. Saxon I can't guarantee and there could be some Teutonic in there as well as Roman.