The valve is the Headlamp Washer T Piece. See Brookhouse
https://classicvolvoparts.co.uk/part...ent_and_Wipers
Probably cheaper from a Volvo dealer. See the Brookhouse delivery charge, and all Brookhouse prices and delivery charges are plus VAT.
It is always worth trying FRF Volvo dealer parts department of Swansea. They often save me money compared to non-dealer supplies. They deliver small parts by post for basically just the cost of postage.
01792 790066 or 01792 784272 - Quoting discount code: C3