I will start by saying I have no affiliation with them however I have home Insurance with Pedal Cover which is a AXA policy but tailored to cover valuables including bikes without the usual onerous restrictions. If I remember correctly I do not have to specify any valuable inc bikes under £15k (per item) and they are fully covered as long as the garage is locked and they are covered for £10k away from home.
Darren (I think?) who runs the brokers is very helpful.
I did a lot of shopping around and could get a similar but not identical AXA backed policy elsewhere for a similar but slightly greater price however it didn’t cover the bikes to the same value either at home or away from home.