If you buy this, go to the hardware aisle and spend an extra £1 on a rubber flange attachment (if they sell it). Without it, you are just pushing water sideways. For the price of a sandwich, it’s better to have it and not need it than need it and not have it.
Only if Sainsbury’s is the only shop open at 10pm on a Sunday. Otherwise, spend £10 more for a proper bellows-style or flange plunger online. sainsbury plunger
I'm assuming you might be referring to a specific product or service offered by Sainsbury's, a UK-based supermarket chain. After some research, I found a few possibilities: If you buy this, go to the hardware
: Once the seal is tight, use vigorous up-and-down motions. The "pull" is often more important than the "push" as it loosens the debris. Only if Sainsbury’s is the only shop open