Screwfix wet and dry are canister vacs, rather like a Henry in style but bigger and noisier and more powerful. You want one with a removable cartridge filter (buy a spare) and you can brush it clean, and, eventually, wash it. Also get the big paper bags, which are the size of pillowcases. They are not essential, but they will catch a lot of fine dust and make the cartridge last longer. If spare cartridges and bags are not available, don't buy the vac. I can't see how the bags would fit in the small one without being scrunched up.
The larger models, with one cartridge filter included, and a power take off socket, are better value than the smallest one. Wet and dry means that it can suck up a bucketful of dirty water, e.g. from a flooded floor or a blocked drain. The paper bags are not waterproof, but the cartridges are. It can also suck up gravel, broken brick, nails and socks.
Aldi may also sometimes have them.
With budget-priced power tools, look for a long guarantee and a retailer that will replace it. If it has a 2 year guarantee, you'll get your money's worth.