As has been said, the records are not at TNA but at London Metropolitan Archives (LMA).
They are not property insurance records, but entries in a register of policies.
A typical entry is 4-6 lines in length, briefly mentioning the type of property and its use (e.g. house, shop, warehouse, brick, timber) and any contents insured (e.g. wearing apparel, furniture), a rounded valuation for insurance purposes, the premium paid and date, and a note of when the next payment is due.
In case it is of interest, LMA offers its own research service at £80/hour.
ask.lma @ cityoflondon.gov.uk