There are certain measures you can take to improve security in your home, such as installing a monitored alarm (choose an NSI, NACOSS, SSAIB or BSIA system), installing window locks, installing 5 lever mortice deadlock (conforming to British Standard BS3621) locks on all external doors. Depending on your circumstances, such as the location of your property, these measures may or may not alter the cost.
However, you can take out a higher voluntary excess (in addition to the compulsory excess), as this will decrease the premium. This means that if you need to claim that you will pay a higher sum towards the cost of the claim.