Question Author
Hi Whoever.
Thanks for your interest.
Since posting this question I have found that the Church IS registered with the Charity Commission, although it took some time to find their registration number.
I have now contacted the CC to verify that "us" as a fundraising body - "us" includes one of the Church's appointed Trustees - can legitimately use the registration number for fundraising purposes.
I don't really see a problem with it, especially as the organ is the property of that Church!
Cheers.