Just testing the water here…
Couldn’t British people’s percieved xenophobia (if this is the case) be attributed to the love/hate relationship british people have with each other? Britain is reasonably unique in that it is actually a union of 4 countries. England, Scotland, Wales and Northern Ireland. We could even include Cornishland if we wanted. The cross border banter between these countries is centuries old and complex, and can appear to be, to outsiders, fairly harsh.
IF this banter is used when describing occupants of other countries it could often be interpreted as being far more malicious than it actually is. What this has done is enabled us to happily laugh at international differences such as accents and stereotypes without it being nasty and make some very succesful comedies that could draw a sharp intake of garlic flavoured breath elsewhere…oops.