Grangers and Nikwax are essentially the same stuff, Its basically just watered down PVA glue.
What BadlyWiredDog said about washing in normal detergent isnt a great idea. It wont harm your jacket, but it will leave residue making any future proofing difficult to adhere to the jacket.
Wash in pure soap flakes or NikWax Techwash then stick it in back in with some proofer. The TX-Direct stuff seems to work for me.
Sprays are only necessary with jackets that cant be washed, or have a liner.