I haven't looked at this for a while (reminds me, must check that our cover is still adequate). However, I have generally found this.
Cycle-specific policies, including cycle-specific additions to home insurance, fall down for keen riders with multiple bikes. Although there is a risk of theft from the home, it's logically no greater than for other valuables stored similarly. Therefore, the key point is the additional risk of theft (etc.) while out and about.
However, few of us are able to ride (=take away from relatively secure storage) more than one of our valuable steeds at the same time. Therefore, policies that just charge you per £10 of value simply don't work for anyone with several bikes.
I've always preferred home policies that let you list bikes alongside other special valuables, and have a general provision that up to £10k (or some other sum that you choose) can be off the premises at any one time and still covered. That lets you take your best bike and a suitcase of other stuff away from home, without having to insure the whole fleet as though you were some kind of weird trick cyclist using them all at once.
Home policies taking this approach are in the minority, but they can be found.