You could tree Green Bee (part of John Lewis):
http://www.greenbee.com/home-insurance
Just scanning the policy document:
Personal Effects
This means clothes and articles of a strictly personal nature likely to be worn used or carried. For example MP3 players, mobile
phones and also sports equipment and pedal cycles. It doesn’t include valuables or money.
Valuables
This means jewellery (including costume jewellery) articles of/or containing gold, silver or other precious metals, cameras (which includes video cameras, camcorders and digital cameras), binoculars, watches, furs, paintings and other works of art, collections of stamps, coins and medals.
So bikes aren't classed as valuables, which have a limit:
The limit for any one valuable will be £10,000.
The limit for any one claim for total valuables will be £20,000.
Home insurance for private residences.
The insurance provides unlimited cover for the total rebuilding cost of your property and/or contents for the cost of repairing or replacing
the contents of your home, but single article and valuable limits apply. It will also include accidental damage on your buildings and/or
contents unless you choose to opt out of this cover.
So it would seem (but worth checking!) they would cover multiple expensive bikes without declaring them.
When our M&S renewal was due I spent ages checking our insurers and loads of them wanted you to declare bikes or would only offer £1000 of cover in total. I eventually lost the will to live and we stayed with M&S.
Oh, Hiscox are meant to be good but that comes a price.