home done respray removal help?

[rawr]

Hello Everyone
I have swapped my Seat Leon with my Friends B5.5...

the car has been resprayed numerouse times buy the old owner and i want to try to remove it all and get it back to its original paint

The car was a lovely dark navy blue but he paid a graffiti artist to make something random,
it looked great but then he had bother from the police, he then done 2 coats of matt black from a rattle can straight on top.. soon got bored of that and went a pastel blue, this was done by a air compressor mixed with thinners, and now its matt white again done by a compressor with thinners mixed both colours done 2 coats

its alot of additional paint on top of this car and i want to bring it back to standard,

any sudgestions ??