I propose an exchange: one set of 30 First-City Coins for one surprise package via the "give a gift!" opportunity card. Instead of selling 30 coins for £7.50, take a chance on a bundle of oddities which can often be worth £10 or more!
Send me the coins, and I shall keep a queue in this thread of users who are owed a surprise package from me, and work on the queue whenever I draw the gift card. If the queue grows to more than a few players, I may use some Fate to repeatedly draw the gift card and clear the queue. Others who seek First-City Coins may post in this thread to make their own queues, and those who have large quantities of First-City Coins may also post to advertise their supply. Be sure to update your posts as soon as you send or receive coins or packages, to avoid misdirected gifts.