I know SC21 fuel tank fits to RC27. But I know there are some people who want to keep his/her vehicle at mint condition as possible.
I just suggest one possibility. Maybe James's next international trip destination is Japan. Maybe his brother in law is a officer of UK consulate at Osaka,Japan.
Or James may win UK lottery.(if so, you can buy two complete RC27s for parts, at 299,000yen(US$2600) at same auction site)
So it is possibility
