The 4 housemates going back in are...

[bigbrothermad123]

Nasty Nick.
Brian Belo.
Rex.
Nikki.
Michelle
This was confirmed by C4, I have seen the advert on E4 aswell.

[Marc]

Nick didn't go in today.. he pulled out and Craig went in. And Dean has been back in as well from BB2..

[Stephanie]

everyone knows they are going in for the task.
:conf:

[DaniBoi]

Only a week late...

[Marc]

They aren't actually going to be the housemates BTW bigbrothermad123
They are only going in for the tasks then leaving.