what power steering pump for zafia Y reg 1.8i elegance?

I need to replace the power steering pump on my zafia Y/2001 reg 1.8i petrol elegance. I would like to buy second a hand one and get it replaced by a non vauxhall garage who quoted for 1200 pds!.
Can anyone tell me which pump type , reference etc..
I am told there are more than two versions , gererations and names, two cables or three and where could look to buy it from.
All I know is the name TWR.
thanks for any help