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 ...
You will probably never know who made the forks or what tubing was used. You have some headset parts but not a complete set. if the dropouts are stamped, it's a hint at the quality. They look good, hopefully you'll get some good use.
it isn't worth a fortune, so you got a good deal, maybe you can double your money.