I agree with Dand2C, They are great!
I also have the Food
Saver brand. I think I purchased it at Costcos. Not Sure what you have in the UK.
I began using vacuum sealers in the 70's when I did alot of winter climbing and camping. We prepared meals
in bulk at home and froze them. The winter weather
kept them frozen until use. It was so much better than freeze dried, the added weight was well worth it.
For Cruising, like dand says the bags are boilable. No dirty pots and pans to wash. I put the open bag in a bowl and eat right out of the bag. You can then use the hot water
for Tea or hot chocolate, cleaning
up , or whatever. Saves water
Great for Beef Stew, Lasagna, Chili, etc.
For sealing clothes and spare parts
etc anything you want to keep dry they are awesome. A great investment, you'll find lots of uses for.
More Things to seal: Extra Toilet paper Rolls! Flares, Documents, Wallets, Cash.
Cuban Cigars, Anything that on a long trip could get wet or damp. You can pack clothes by changes at home..and food by portions.
The bag is welded shut ( heat) after the air is removed. If you cut the bag open just below the weld, you can reseal the same bag.