I agree with djr33, sociolings has become very popular in recent years. I'm currently in my 2nd and final year of my sociolings masters at Goldsmiths, university of London. Although I don't have experience studying there, I would highly recommend Lancaster uni, which has some of the leading researchers in sociolings. From experience though, I'd say that the larger the department of sociolings, the more support opportunities there will be. I know it sounds counter-intuitive, but the bigger the department, the more funding it may attract and so there would potentially be more opportunities to be involved in the department.