Hi Id and Ego seek,
Thanks for your interest in Linguistics. Yes we normally require students to have Maths and a foreign language at GCSE for all degrees involving Linguistics however we don't specify a specific grade so don't worry too much. To get an offer, it's much more important to have AAA/AAB at A2 level, or equivalent, including English Language, or English Language and Literature, or a foreign or classical language.
All the best,
Fred