Among the actors who acted in UK movies, what percentage of actors received a rating of at least 3?
UK is a country
SELECT CAST(SUM(IIF(T3.a_quality >= 3, 1, 0)) AS REAL) * 100 / COUNT(T1.movieid) FROM movies AS T1 INNER JOIN movies2actors AS T2 ON T1.movieid = T2.movieid INNER JOIN actors AS T3 ON T2.actorid = T3.actorid WHERE T1.country = 'UK'