Someone here recommended Miltons baby fluid a while back. The stuff used for sterilising babies' feed bottles.
I haven't tried it myself as I've got a metal header tank, fitted a new uprated m/cylinder which is still clean and as for the washer bottle, well the rest of the engine bay makes it look clean........ Bleach might be a touch too caustic?
Adam
TR7 V8 DHC Jaguar Solent Blue. 9.35cr Range Rover V8, Holley 390cfm, JWR Dual Port, 214 Cam, Lumention, Tubular Manifolds, Single Pipe Exh, 3.08 Rear, 200lb Spax & PolyBushes, Anti- Dive, Capri Vented Discs & Calipers, Braided Hoses, 4 Speed Rear Cylinders, Uprated Master Cylinder & Servo, AT 5 Spokes and Cruise Lights. No Door Stickers. Mine since July 1986, V8 from 1991