My 2 year old son will go to sleep at bed time, but wakes up several times during the night!
I have put a stairgate in his bedroom doorway, but he just climbs over it and comes into our bedroom.
We've tried holding the door shut, but he screams and bangs on the door.
I'm at my wits end and soooo tired. Just don't know what to do?? :(

Does he still take naps? If so, maybe shorten the time, or make it earlier in the day.

He doesn't have a nap anymore and is very active during the day.

What is the bedtime routine like?

Children need routine and structure.

If you have the same routine night after night, you are going to have to get tough and keep returning him to his bed consistently. Reassure him that everything is okay and that big boys sleep in their own beds.

Holding the door shut is not a good idea. You are scaring the poor child.

He has a good routine at bedtime and is always in bed between 8-8.30.

I keep telling him that big boys sleep in big boy's bed and always put him back and stay with him until he falls asleep. He has a bear that sings lullabies, so always put that on. He will go back to sleep, but then wakes up a couple of hours later.

When he wakes up... take him back to bed. You have to be consistent. This is the age when a child's mind is constantly working. There are things to be done, toys to be played with. They need consistency.

Maybe try giving a nap early in the day and putting to bed later in the evening.

Should I speak to him when I put him back to bed or put him back to bed in silence?
Also should I leave the room as soon as I put him there or stay with him until he's asleep?

Do not speak to him. He still may be in a dream state. Just take him by the hand and lead him back to his bed, put him in the bed and leave.

This may take a few days of crying, but it's well worth the torture. Just be consistent. Do the same thing every time.

Thank you for the advice, will try and persevere! :)