Gidday Alan,
You'd need the original links for the lower suspension in order to convert back to original ride height. Hopefully, whoever sold you the bike has these if they lowered the thing. I doubt any of the dealers would carry these links in stock so, if you don't have them you'd have to get one of them to order for you. Other option is to put the word out among exisiting F650 owners who may have also lowered their bikes and see who is willing to give up original links.
All the best.