At your sons age I was academically gifted but pathologically lazy and had no real idea what I wanted to do. I started A levels (Maths, Applied Maths and Geology) but left after a year. I would have gone on to a maths degree and a solid future in accountancy, my sole source of joy being a slightly amusing tie 🙁
Instead I completed a 4 year ONC/HNC engineering apprenticeship with Marconi. Found purely by chance from looking at job adverts in the local paper. At the time they also had student apprentices who’d done A levels and were being supported through their degrees. These guys worked outside term time and did a year in the business in the middle of the course. Do you have any large engineering employers locally who offer these opportunities? I remember the wages being pretty savage so your boy may need to stay at home. Our student apprentices had subsidised accommodation though.
The four years gave me a good understanding of what I might enjoy doing because it was split into 3 month placements across a variety of departments (test, test eng, design, QA, purchasing, sw lab). I left to go into audio electronics and now run the test department of a hi-fi company, a job I love doing. I would require a degree to work in R&D but could be supported in this from my current position. 2 people in my department are currently doing day release degrees.
Unless your lad shows interest in a trade, I wouldn’t see the vocational courses as a great option. Junkyard is likely to be the best source of unbiased information.