The PCA lacks of a few Viking Age samples due to being too bad thus canceled by the outlier check. British Viking Age samples look like to be German, but I should remind that PCA is based on dedicated components rather than genetic similarity in basis of the whole genome. Let's see how those samples look in a formal analysis. I have made several tests to give different views, for the reason that populations don't place in tests on one or two dimensional axis.
We see that in formal tests Swedes are closest to British Viking Age samples, followed by Irish and Scottish samples. One straightforward conclusions could be that those Viking Age people were mixed Scandinavians and Celts/Britons. One bizarre remark: Swedish samples are on the PCA prone to bias towards Finns and Norwegian samples show less this kind of similarity. Still Swedish samples are closer those Viking Age samples from UK. I have not tested this curio using formal analyses, but as far as I know this will be true in all tests.
edit 11.6.2017 12:50
German samples are from Leipzig.