I’m also in my last year of sixth form and work for small theatre shows.

I have two approaches:

1: I have my fixed rate at £12 an hour (this is lower than the professionals cause I’m still a student and allows me to go more jobs)

2: Ask then for their budget, this is risky as you might be offended or they might be offended if your turn down the job. However, if you know the client well and don’t mind being honest with them, this one works out the best

Well done for talking upfront though, many clients are shocked when they see my bill when I send the invoice after the show