You're very unlikely to get agreed value cover on a daily-use bike - it's generally available only on classic policies which require that (a) the bike isn't your main one, and (b) you cover only a limited mileage. Many classic policies also require that the bike is standard spec - Wilbers and HID lights wouldn't count as standard, I expect.
Take lots of photos of the bike showing its condition and keep these should you be unfortunate enough to suffer a total loss - they will support your claim for 'top book' price. As for things like the Wilbers, lights etc you can get these covered as accessories on most regular bike policies, but how they're dealt with varies depending upon the insurance company.
I'm with Equity Red Star through Carole Nash and they were happy to increase the cover on my Bandit to include around £1600 worth of modifications (mostly performance-related) and this cost only a few pounds more despite the 30% increase in power. Had I suffered a total loss, they'd have paid me £1600 over the agreed market value of the bike. However they wouldn't cover suspension on the same basis, so I've had to pay £60 to cover my Wilbers over and above the value of the GS. I did point out that this seemed expensive but they said that it was a mid-policy change, and that when I renew they'll find an insurer that will cover the suspension for a much lower additional premium.
Talk to Footman James and ask what's the best way to get adequate cover - they'll be able to advise you better than anyone here because they know all about you, your bike and your existing insurer.
