l am a beginner with no qualifications but l wanna get into car modification and car audio.what course should l take?l live in the UK

you ideally would need a city and guilds in repair and servicing of motor vehicles, city and guilds in automotive electrics and then a try and get a job. there is no money in it until you are qualified as vehicle modding can include spraying which takes years to master. bodywork which takes years to master. l do not mean to put you off however there is a lot of work involved and you have to have a serious love of cars to achieve this.
good luck

SQ Plus do a course that you can take part it. they teach you all you need to know about car audio and fabrication. decent course and it does not cost the earth.
obviously you wont have a proper qualification, but if you want to know what u need to do i'd recommend it. if u want to start your own company then do what the bloke said above.