Checking my emails - Parcelforce was £13.30 uninsured, and Overland Express was £45 with £750 insurance.
I've used Secursus in the past, but not sure I'd use them now. Has anyone made a successful claim? See https://www.thefretboard.co.uk/discussion/270188/secursus-insurance-not-valid , linked from https://www.basschat.co.uk/topic/498649-secursus-insurance-not-actually-covered-without-certificate-of-sale-physical-signatures/
"They finally confirmed that for their insurance for individuals to be valid they need to give prior approval in writing, they also require evidence of payment for the item, and they need a certificate of sale"