What OOF needs is its own currency which we will call an Omega which is worth a nominal £100, this is split into 100 Astras or a nominal £1, which in turn is split into 100 Corsas each worth 1p.
Now Omegas are used as a currency between say me and a member to buy me a real Omega using 2 paper Omegas, I then use 20 Astras for a second hand coil pack in the spares section, followed by another Astra to relieve STMO of having a wrong coloured Astra, who in turn uses 50 Corsas from his Astra to purchase that Corsa keyring he was always needed in the wanted section. Now the genius of the system is the currency is only of value to OOF members, so nobody would have any incentive to rip anybody off like when using £'s, as if you are banished from OOF your Omega, Astras and Corsas are all worthless. Because there will be no inflation measure 5 Astras will not only buy you a Goose from Lord Opti in the spring, but the Goose will still cost you 5 Astras in the autumn. All of the spare paper money will be stored in the OOF central banks, Tuby's garage where it will be 100% safe from 3rd party water damage, fire and theft.

See the perfect solution, what could possibly go wrong?

Sadly, not a Rods original idea, the inspiration came from reading this article about a Russian farmer, who created his own currency for use amongst friends, but the Russian central bank has decided it is a threat to the rouble and must now be eliminated.
https://meduza.io/en/feature/2015/06/12/do-not-pass-go-do-not-collect-200-dollars