On Waitrose website it says free click and collect if order is over £30
Looks like you might not need a vet's prescription for the Advantage Cats spot on treatment either at Waitrose, which saves £15 or so, depending on how much your vet wants for writing one out.
You can do a free click and collect from any Waitrose store if you don't get up to the free delivery amount (£30)
8% cashback with Quidco with a 100% tracking score
You have a link ?