Studio Etiquette regarding recording

Next week our band will be rehearsing in a studio that is both a recording studio and a rehearsal studio.

Apparently they can record your rehearsal and give it to you on a CD. I'm sure this would cost extra. The recordings I make are disposable - I listen once, maybe twice, just to see what's working and what's not.

In general, would it be considered poor form to record the session yourself on a portable recording device?

I have zero experience in studios and I'd rather not irritate them our first time out.

I'm thinking, if you paid for rehearsing only, that is all they should expect. It's really cool they offer more, but if you did not contract for more, why can't you bring your own recording device. I'm sure every band does not want to pay to have every rehearsal "professionally" recorded. So bringing in a smaller recording device should not be rude.

2 cents.