24!!!! You're just a nipper.
I started flying when I was 27 (at EGHI as it happens). Initially it was just as a hobby but I always had the idea of commercial flying in the back of my mind. I made the decision to go for it when I was 28 years old. I'm now 32 and I've been flying 737's for 9 months now.
I also know of a 737 pilot that didn't start training until she was in her 40's so you really have nothing to worry about.
SW