"Unable to get a place on parentcraft classes at LGI"

I sent off a parentcraft booking form (LGI) when I was 7 weeks pregnant. I was aware these sessions could get fully booked, so thought I'd have a chance if applied early.

I have received a letter, 13 weeks later saying all the sessions before my due date are fully booked. I would like to know if the places are allocated on a first come, first served basis, or is there any other critera they use?

Are there people who booked after me, who have managed to get a place?

I am quite disappointed, and wonder if it would have been better to book by phone, although I wasn't told this was an option.