Right now you have a "worth" of 3 pounds, because it was "worth" it to the seller to have 3 pounds, and you thought the forks were worth parting wiht 3 pounds for.
If you weren't there, the worth would be 0, and if multiple buyers were there, the price would rise until only one was left. That might be 4 pounds or 400.
Worth or value is what someone is prepared to pay for an item.
They're nice-looking forks and provided there are no cracks, dents, or damage I'd totally ride them. You'll need a bike with a matching headtube and cups that fit the headset.
Also, its hard to get the scale from the photo but either the steerer tube is really long, or the fork tines are short. It could be for a 20" or 24" wheel - I suggest you fit your expected front wheel and then see if the brakes reach, before disassembling any headsets.
Brakes are super-critical, and front brakes even more-so. Don't be tempted to go without front brakes if they don't fit.