I think Chris is correct, your buildings ins may cover the risk, so may your employees liability if you are commuting and an annual travel policy almost certainly will provide cover.
The potential hazard is large (millions) but the risk is small (not many cyclist are done). As well as CTC there is a growing number of private firms offering cover, cycleguard, zurich.
You pays your money and takes your chance, or not.
Some big companies are deciding if you should worry about this enough about this or not to pay £100 a year.
Imagine if Direct Line started running tv ads saying " do you know how irrisponsible you are being an un insured cyclist"??
Before you know it they have replaced the bank charges money with some cycle premiums!!
and those who dont insure are letting everyone down. Shame on you!!