Northbrook has a decent rep. I’m up in Crawley.
I can’t see how that course would be any less well regarded than doing A levels tbh as it’s quite specific and vocational.
The extended diploma is worth the 3 A levels worth of credits.
Alternative if he wanted to have a broader set of qualifications would be do that course at just ‘diploma’ level (worth 2 A levels) and another different course too. Maybe another BTEC at sub diploma (worth one A level), or do an A level
too in something related (ie maths/Ict/physics).
Some uni’s like an A level along side Btecs to show an aptitude for exams. Worth checking with a number of uni’s you might be interested in.
Otherwise…… Looks like a good move.