Be worth what someones willing to pay, personal i'd pay about 60-80 for it but thats because althought they're a really nice fish not my main type of fish, if you get somone who's well into their eels and monster fish you might get somone paying more.
If you do come to sell if i were you id' offer postage as it'll sell a lot better. Me to drive to Derbyshire and back would cost me near on 70£ in Fuel where as postage would be £25 makes it alot more sellable!