youre probably looking at around £150-200 and
maybe £200-230 at a real struggle because anything above that puts it within range of
Decathlon's entry level triban bikes and they are kitted up with newer hardware making it a better proposition if one was to spend money.
Obviously condition of the bike and any upgrades done to it will factor into the final price. Im just basing it on stock setup and it was about £600 new.
This is my opinion however and other members might think differently but i wouldnt pay a whole lot of money for your bike