Midwife led units are just that, led by midwives, you will not see a doctor at any point throughout your labour unless there was an emergency and it is connected to the main hospital for the, to attend in such an emergency.
Pain relief options normally include: water, gas and air, pethidine.
Consultant led units are that, led by doctors, midwives care for you but doctors are available if needed, ie for forceps, ventouse, c/s, epidural. If you are on a consultant led hit you can still have a low risk birth but you will more than likely end up on a CTG monitor, if you are induced you will be here aswell and if you are classed as 'high risk' however you do have a choice in all matters of your care even if it is 'recommended' you do something there is no person who can force you to do anything you don't want to do.
Some MLU are connected to a hospital consultant led unit which means if in labour you wanted an epidural or there was a problem you can be transferred, some are stand alone so transfer would be via ambulance.
Hope this helps,
Oh and of course there is home birth which is my choice :)