Hi Leon
I suggest that you go out today and find a comfortable spot that will give you a good view of the area where you saw the tracks, dont go into the area that you want to observe keeping disturbance to a minimum. With the mornings getting colder deer prefer sheltered south facing slopes that get the early morning sun.
At the first opportunity get out before first light moving into position with the least disturbance checking the wind direction as you go ideally you want the wind in your face but things are rarely ideal.
Be patient the deer may not move for an hour after first light, use your binoculars to look into the bottom of the undergrowth, look for the line of their backs and twitching tails these are the giveaways.
Muntjac are quite tolerant of people but the less you disturb them the more you will see of them.
Take something to eat and drink as it may be a long morning.
Remember Shape, Shine, Shadow, Scent
Shape: dont allow your self to be silhouetted and leave adequate cover between you and the deer
Shine: early morning make sure that the sun is not shining directly off any of your kit including binocular lenses
Shadow: this can give away your position to crows etc. early morning who will jink and make an alarm call if they see it
Scent: watch wind direction, if you are on lower ground as this warms scent will rise
Hope the above is helpful, good luck, Pothunter.