A quick update on this. Caledonia Investments had its AGM last and was seeking authority to spend £75,000 of shareholders' money on Tory campaigning in marginal seats. You can find the results of the AGM here (PDF), the resolution is number 17. The bottom line is that about 20% of votes did not support the resolution (about 16.5% of that being votes against, the rest abstentions). If you include the fact directors and the Cayzer Trust own 30% plus, that suggests that the actual level of independent shareholder opposition was higher.
But that means that there must be fund managers out there which actually voted in favour of partisan political donations. I think we can probably assume Fidelity are in that club, but who else? If you are a trustee of a pension fund with any more in Caledonia ask your manager how they voted.
It also appears that a few charities may have money in Caledonia - I wonder how this has gone down with them?