TBH, your looking at the wrong stuff...we do this type of work all the time and its all down to what you are trying to achieve....

Sound deadening can be done in three steps...

Layer 1 - Is usually a self adhiesive matt with bitumen. This is applied to all panels you want to reduce noise from. Note, it is NOT necessary to cover panels with 100% coverage, even 30-40% coverage of a panel will be more than enough. This layer is there to reduce to vibration in the panels hence reduce the ringing and drone you can typically get in a motor vehicle. This is also the layer that makes the panels sound solid rather than have a ring to them. Tap the outside of a sound deadened car and you will here a thud.

Layer 2 - a Closed Cell Foam. This is an isolation barrier and helps absorb some road noise. Just by using layer 1 and 2, people notice a significant drop in cabin noise. usually comes in 6mm/10mm etc

Layer 3 - Mass Loaded Vinyl, this rejects air borne sound coming into the cabin. You need the proper mass loaded vinyl rather than the hybrid composite stuff you can usually find on amazon. This is the ultimate in noise road rejection.

If you strip down a high end car like a Mercedes, BMW, Jag etc, their foam layers are VERY thick and then topped off with a MLV...this is how they get the cabins so quiet. Unfortunately, the thickness of foam is not suitable for most vehicles as BMW etc designed the floors with the thickness of the foam in mind.

If you are looking into just replacing what was originally on the floor, then Layer 1 would be enough. If you want to go above and beyond, then layer 2 and 3 can be looked into.

The above is the PROPER way to do to it...and the proper way means spending more than £13 unfortunately

If you need any help feel free to PM me