8th October 2011, 03:05 PM
See the recent Oxford Unit Lankhills mongraph, similar sort of date range for 'foreigners' in southern England - if my pet isotope project ever gets off the ground it should (hopefully!) pad out the number of 'outsiders' in northern England in the 4th century. They're certainly out there (there are almost certainly loads lingering unidentified in museum stores too), the only hassle is getting the funding to find them