Exclusive has aircon, heated electric mirrors, electric front windows, 16" wheel trims and cloth seats...
Sri adds front fogs, 17" alloys and sports cloth, (think MV6) options include parking sensors, leather and Exterior Pack/XP which adds 18" wheels and body kit... looks alot smarter than it sounds, especially in white or dark grey met.
Design adds 17" alloys, single zone climate control, electric rear windows, 6 disc cd changer in head unit, half leather seats with better adjustment, trip computer and cruise control.
Elite adds dual zone climate control, full leather, with heated fronts...
Nav models have full colour satnav, with upgraded stereo. Adaptive xenons were available on SRi up, but very rare option... only ever seen one car with them fitted...
If you're going newer, post 2012, range reduced to Exclusive and Design... both available with Nav, Design now has parking sensors all round, heated front seats and, I believe cloth seats with better adjustment than the Exclusive ones...
Hope that helps