Hi there,
I had DS on a midwife-led unit so can't really advise on how things work on a labour ward, BUT one thing I do know is they can't actually make you go home even if you're not in established labour. If you refuse to leave they can't force you. You'll have to hang out in a waiting area somewhere though, as the likelihood is, they won't give you a bed.
Still safer to be at the hospital though, IMHO, than risk having a baby in the car as someone from my town did when they sent her home despite it being her second baby! And my nearest maternity ward is within 20-30 min drive.
Would be tough if you ended up hanging around for some 24 hours though 
Have you thought of staying somewhere close to hospital, is there a hotel or B&B nearby that you could go to if they were to try and send you home, or where your DH could stay? Could you afford that?
The official policy in my hospital is they won't let relatives stay overnight after the baby's been born. That's even on the MLU with single rooms, no mind on the general multi-bed postnatal ward where ladies stay after giving birth on the labour ward. That said, we got the impression our midwife might have let DH stay if I had decided to stay overnight.
I think it may depend on individual people, as we were also told that if we got completely stuck for childcare 2nd time round, sometimes the MWs would allow DS to be present at birth but that's really up to who you get, and how well behaved he'd be.