Guys thanks for your replies... Called one of my localish dealers and found they had the 520 kit of sprockets in stock for my ZX, so I went in and picked them up and when I got home realised they were about 2/3rds the thickness of the current ones

not knowing what had happened I took my sprocket in (the original) and showed them.. they couldn't figure out what it was as it was thicker than 520, 525 and 530 so again

dunno. Any I decided to buy a new chain to suit as well because I've only had the bike a week and although I was told it was only replaced 1000kms ago I have my suspicions it was not good because it had never been lubed in 6months/1000kms and there were a lot of other neglected parts of the bike like hot tyre pressure (had to test as soon as i got home) 15psi front and 25psi rear hahaha.... So long story short it really does have a 520 conversion now and brand new front and rear sprockts with an RK Gold chain.