I also have my instruments insured on my household policy.They are also named so that certain instruments I take out of the house are covered for use at gigs ,sessions etc. Royal London Mutual Insurance.
As the policy covers all my possessions up to a figure of £1500 then it is worthwhile taking instruments off the named list to reduce your payments, if their value goes below this figure.
I approached Royal London to see if they would be interested in a membership Insurance scheme, but there was no interest. This does not mean I shall not try again.
Al