UK spec has the speedometer in Miles Per Hour, the Jap spec ones have it in km/h.
Some Jap spec 525i's are actually rebadged 523i's, so be careful.
They have 2.5 litre engines listed on their registration cards, so many dealers just swap the badge out on the boot.
Also, Jap spec cars tend to have higher specs - most will have the higher spec OBD, cruise control, electric seats etc as standard - the Japs love their toys! - LOL
Many UK spec cars on the other hand will have manual seats, basic OBD, no steering wheel controls....etc.