Thanks for the reply.
As I am only in China for the transfer I did not intend to have any RMB with me nor use an ATM and have any RMB left over just before my departure from XMN.
What do you think of XiamenAir's 3 options? Ignore them all and just get a taxi into the city instead, if so I will have to read up on getting the 72 hour transit visa unless my 2 year UK tourist visa already covers me?
If your visa is valid, of course it covers you. If not, the fact that you've been offered options 2 and 3 suggests that you would be provided 24 TWOV (so you can leave the airport).
I agree with jansoncheng wrt going it alone. You can connect a credit card to didi for your transportation needs, though I don't like taking didi from airports or train stations, and just pull out Y300-500 from an ATM, unless you plan to be a little more extravagant.