Even though your property is empty, it may still be full of fixtures, fittings, and furniture, so it pays to make sure that you are covered in this area. This is of particular use if the contents in question are of a high monetary value. While a separate policy might make sense for some, a broad policy that includes contents might make more sense. Be sure to read the small print to ensure you are appropriately covered.
For most properties, subsidence is not an issue. If it is, and you are leaving your property vacated for a prolonged period of time, the damage that accumulates can be substantial. The costs of such a policy can therefore be high, particularly if the property has a history subsidence, but when compared to the value of the damage that such structural issues can produce, they are relatively insignificant.