Is it loose or carded ?
Loose you have overpaid. Carded, an 80 is decent enough - I don't know what the UKG fees are and how much you paid for postage but I would expect it to be worth about £80-£90 with an 80 UKG grade
I suppose you have to look at it as to why you got it graded. If you did it to preserve it and keep it in your collection or because you like graded items then it is all good - if you did it to make a profit then I don;t imagine you have made much of one.