Replaced wiper motor and arm all well but water cascades down rear window rather than jet. So im thinking replacing the nrv will sort. I imagine that it can be from any car once it fits pipe etc? Present :2008 TDV8 HSE
Gone Audi A5 2.7TDI
Gone Discovery 3 HSE
Gone Mercedes CLK
Gone Range Rover 2.5 DSE

This will fit.

http://www.ebay.co.uk/itm/Screenwasher-Non...1309227783

The NRV only stops water draining back down the pipes to the tank. If the water is cascading down the window then there is plenty getting through. It sounds like the jet nozzle might be missing or something is not connected to it correctly. Previously..
Vogue SE TD6
Defender 90 2.4
Defender 110 TD5
Vogue 3.5 EFI

+1 for contraband.

Nrv will not help you. Only stops the water running back to the washer bottle under the bonnet.

Check the new arm is fitted correctly, as that should have the jets in it, I think......

 2011 Range Rover Vogue SE 4.4 TDV8

Previous cars :
2003 Range Rover Vogue TD6
1999 Discovery Td5 ES
1995 BMW M5 3.8 6 speed
1992 Range Rover 3.9 Efi Vogue
1992 BMW M5 3.8
1988 BMW 735i SE
1989 Ford Sierra XR4x4 2.9i
1981 Ford Fiesta Supersport

Jets look fine and are brand new as is arm .will check it out thanks chaps  Present :2008 TDV8 HSE
Gone Audi A5 2.7TDI
Gone Discovery 3 HSE
Gone Mercedes CLK
Gone Range Rover 2.5 DSE