With respect, how much experience do you have of our towns and cities outside Devon, which as far as I know isn't exactly a hotbed of immigration.
Let's see, I used to visit London (specifically Clapham, in the Lambeth borough, which has a very high diversity rate) weekly. When I was younger, my mother was heavily involved in working with ethnic minorities in Ipswich (specifically bangladeshi mothers), as well as her wealthy white practice, as a community midwife, and I've seen the results, good and bad, of the sort of leadership employed in such a community.
I regularly visit towns and cities all over the UK, and with the exception of Birmingham, I've never felt uncomfortable in the presence of large numbers of ethnic minorities, and Birmingham is a city with no redeeming features anyway, irrespective of it's areas of non-white friendly attitude.
Is that enough?