I'd certainly want to keep it if at all possible, without it the back end will feel a lot looser...
It's definitely a standard part that comes with the chassis pack for that car and I can see that it would be a lot easier to remove it than it would be to replace the bushes in it.
To be on the safe side contact the makers of the kit and see what they say (they'd also be the people to talk to about getting replacement bushes)
http://www.ngcars.co.uk/default.asp?PageID=9