Hi Boobylicious! When I was pg with dd1 I was petrified, kept thinking how on earth will a baby fit outta that space. I mean I was really freaking out big time. But you know what, I told my fears to a lovely midwife - she asked me if I had any younger siblings, when I said yes, she replied "well there you go then, if it was THAT bad, do you think your mum would have given you a little sister?"
She then spent ages with me writing out a lovely birth plan that ended with the sentence "If its all too much, I want a Csection."
Well, my birth plan didn't need that, in fact from being the biggest wimp ever, I actually gave birth to a 8lb baby who was lying back to back after 44 hours of labour that finished with me being induced. The only thing I used was a TENS machine, breathing and relaxation (I actually watched Match of the Day inbetween pushes). I wasn't being brave, nor a martyr, I just managed to get by on that. I think because I was so convinced it would be awful, when it actually happened, it wasn't as bad as I had expected. DD2 was born just 1 hour after contractions started, again with no pain relief.
Good luck with whatever you decide, but if you can face it, it really is worth giving it a go, and you can always ask for a section if it gets too much.