I think this incident highlights the dangers of large non-standard visual circuits. Both aircraft in the visual circuit were outside the ATZ on the base leg. The second aircraft was told to position behind the PA28 with the inevitable result of extending a large circuit even further. It is not uncommon to see Coventry based aircraft with trainee pilots who have less than ICAO level 4 English flying Bomber circuits at nearby airfields. A pilot on an ILS is not expecting to encounter circuit traffic on a 3 mile final, lookout would be directed towards the base leg at about 1 mile. We have to educate pilots to fly correct circuit patterns and not extend downwind. If a student can't fly a proper circuit they should not be flying solo. If they can't speak English they shouldn't be flying at all.