I would hope English referees are unbiased. Wales have got one again this weekend against Scotland. Maybe any bias will be against Scotland for beating England last weekend.

In fact, for the remaining 12 games the appointed referees are from the following countries:
England      (4 matches)
France       (4)
South Africa (2)
Scotland    (1)
Ireland      (1)
Round 1 last weekend had two English referees & 1 Scottish, making the predominance of English referees even greater, covering 6 out of 15 possible matches during the competition.