Because most Imax cinemas in England, aren't proper Imax screens
They're a bit bigger and curver than the normal large screens, but real Imax is much much bigger
http://www.slashfilm.com/qa-imax-the...+%28%2FFilm%29
http://maps.google.com/maps/ms?ie=UT...6c5915161c3667
out of date but some good info
http://destroyfakeimax.blogspot.co.uk/