Under the scuttle panel. Once there you may just be able to manipulate the hosing enough to leave the NRV located underneath the small mesh panel which will avoid you having to remove the wipers and scuttle panel in the future.
While you're in there though it's a good time to lubricate the wiper mechanism and clear out any dead leaves/vegetation at each side by the bonnet hinges
It will indeed as the lack of NRV will see fluid and pressure going back against the flow - towards the pump. Look a little further down towards the front end of the scuttle panel and there should also be an inline NRV for the rear washer as well.
Doris the 1998 Portofino Blue 20V Bog standard needn't be boring...
Yep I think so... It was a T one, inlet on the bottom outlets to the sides. However it was so 'strong' I couldn't blow through it and pump couldn't work it I guess. Pushing a small screw driver up it I could feel the spring inside and it was pretty firm...almost like a mini dump valve....guess it was just too strong!! Inline valve I fitted works fine!! Bit weird!!!