Storage heaters will offer a 'background' temperature that can help in frost protection but they're slow to respond to changes in temperature which could lead to under or over heating (and excessive running costs etc).
A mix of both storage and direct (tubular heaters) may be the way forward but again, a delicate balance is needed to avoid excessive temperatures and the associated extra running costs.
If frost protection is needed for water pipes etc, then these areas need to be protected by the tubular heaters. Unfortunately, there is no complete answer to this and a trial of storage heaters may be the way forward?