Even if you do get something, how will you know that they are the real thing?
At the very least you should see a signed accountants certificate that reads:
In accordance with instructions given to me, I have prepared, without carrying an audit, the annexed accounting records of the British Airlines Stewards Stewardesses Association and from information and explanations supplied to me.
Signed
(Accountants)
If you get a summary copy of accounts that later proves to be false or wildly inaccurate as a result of a subsequent audit then there are serious consequences for both the association and the accountants.
The whole subject of trade union finances is very well laid out on the following website and do follow the links to drill down a bit deeper.
Trade union finances and accounting records : Directgov - Employment