The literature I was given at hospital last week gave 4 things that will increase the chances of successful vbac:
Having previously had a vaginal birth
Going into vbac labour naturally (eg not induction)
Your previous section was elective (not emergency)
BMI was less than 30 at start of pregnancy
Women who meet all the above have a 75% success rate according to the pamphlet (but remember a healthy woman in first labour has 20% chance of ending up have emergency section, so yes worse odds in vbac but not that widely different).
For me only the BMI counts as I have had one baby by emergency section and this time because I'm high risk of pre-e I must either be induced early or have a section. For me I've made my mind up to go for a section but it's everyone's personal choice. Before my section last time I'd had 14 hours of induction and nothing started (though the section was because blood tests showed I was more seriously ill and no more time to waste). My doctor said this could mean a future induction may be more likely to be unsuccessful too.
Have you got a consultant appointment lined up due to previous section? They should be able to talk you through. I was worried I'd just get pushed one way or the other but mine was very much of the opinion it was my decision and she just went through the facts and answered my questions, she was really helpful.