where can I buy badminton racket in UK or online?

I'm studying in Newcastle and walk around London before coming to Newcastle, and noticed that London doesn't any have badminton stores.

I found one store near here and they don't have what I want.

Are there any place that I've missed? and are there any suggested sites that's trustworthy to buy from?

Specifically, I'm looking for li-ning flame n50 (and would be much appreciated if I can choose the string)

thanks in advance!