So you save £13 now. Then later, when the (ebay) potentially fake/substandard/poor-quality, one fails. You then static (ESD) damage/destroy a £1,000 unit, for a big customer. They get annoyed with your lack of quality, and cancel a £35,000 order. Also, you lose hundreds of thousands of pounds in lost, future business from that now unsatisfied/annoyed customer.
Wait a minute, I forgot. You're a hobbyist ONLY. So, no problem, as no customers, and no expensive devices, that may get damaged. Only a £0.03 (3 pence) non-DC rated fuse, which you saved 3 pence on getting the correctly rated fuse.
As a hobbyist you only saved a total of 3 pence on the fuse, as you only needed one of them. But the pennies eventually add up, over time.