The exclusion of racing is probably less to do with the risk of theft, and more to do with the risk of damage - to you bike and to third parties if the insurance covers public liability.
The insurance I'm looking at is with E&L, and is about £80 a year, with £1m public liability and roadside recovery cover and replacement bike hire. It covers road based time trials, but there is another policy they do for competition/racing.
My household insurance wouldn't even cover half the value of the bike, never mind anything else.
Edited: 02/05/2012 at 09:50