Bella - I had a 3 year gap between my first two and I was paranoid that I was going to forget my HypnoBirthing techniques, even though I was doing revision exercises and added mantra music to my labour plan! I needn't have worried - I kept all my kick-arse training in my subconscious and it came back to me beautifully at crunch time. I knew I was going to be ok, even though the labour was quicker and more intense and I left it to my body to do the work while my brain concentrated on breathing. By the time I felt my baby's head coming down with my finger I knew I was home free for that vaginal birth Intense, but home free.
Once your body has done it once, all those muscles know even better exactly what to do. It's up to what the baby is going to do and how you let your body do it, if all is progressing normally. If things aren't progressing normally then your MW will know in plenty of time for a transfer - she'll know the signs even if you don't.