I left school at 16 and did an apprentiship 3yrs i got a BTEC national cert in motor vehicle engineering , a NVQ 3 in motor vehicle diagnostics , Repair and maintanance
Worked for a couple of years then went off to uni and basically experianced what Slick did
they didnt cater for what i needed to know i was recovering things that i learnt at 16 and then doing math and engineering science that was WAY too difficult for me to comprehend
As for starting out i knopw what i was leaving school i started applying for apprentiships now , try wrighting to as many places as you can , explain your interest , many places will apreciate somone that WANTS to do the job instead of endind up with some plank , i remember i place called BK international dealt with honda , jaguar , and some other main manufacturers could google them see what comes up
as a word of caution tho , when i was working in garages i found it quite hard to find the motivation to work on my own car , you might be different , an if you do get yourself an apprentishop be prepaired for a bit of frustration at collage youll be there with mainly 16yos many without a care for cars or learning anything (tho most tech collages have hair n beauty courses there so that sometimes makes up for it)
last of all good luck , i dont twirl spanners for a living anymore but still got all my pretty shiney tools to use on whatever i want