I'd check that the difference between your quote with physical security devices is enough of a saving over a quote without them to be worth it. Back when I lived in the UK, I found that the differences in quotes weren't actually substantial. Though YMMV.
I've heard all kinds of nightmare stories about people's bikes being stolen while they popped into a shop for 5 minutes for a chocolate bar and can of pop and insurance companies not paying out because the owner had declared that it would be secured with a chain while unattended and it wasn't.
That's not to say that you shouldn't use security devices, but I'd recommend that you only declare them to the insurance company if you really are prepared to attach them every single time you turn your back from the bike. If declaring them only saves you 50 quid a year, I personally don't think it's worth the hassle.
My other half rides horses and once had both her saddles stolen from the horse yard. Unbeknownst to her the small print on her insurance had changed slightly between renewals and because she hadn't told them the exact value of the saddles they only paid out around 20% of the value. So I'm familiar with their low behaviour but hadn't factored that into my own process!
I've battled with security options over the years, and now I simply just wrap a big old chain and lock around the crash bars. No need to have to remember it when I leave home and the key is always with the bike's ignition key
No - I didn't end up buying one. Mainly because the insurance company I used weren't insisting on a lock but also because I needed the room under the seat. For such a big bike there is an amazing lack of space to put anything unless you farkle the thing!