Above ground drainage
Are there any stains on your rainwater or soil pipes or damp patches around them on the brickwork?
Have any pipe clips or straps worked loose and require replacement?
When was the last time that the pipes were rodded to ensure that they were free running?
Are the rodding eyes accessible in case there is a blockage?
Below ground drainage
Are all the rodding eyes accessible?
Are the inspection chamber covers accessible and can they be lifted?
Are stop cock covers accessible?
Do you know where they are?
Are there any gulley covers that are broken and have all leaves been cleared from drains?
External services
If you have external exposed water pipes, is the insulation still in good order or should it be replaced to prevent freezing in the event that we have a severe winter?
Internally
If you have an insulated loft make sure that the insulation does not block any eaves ventilation and does not extend below the cold water tank.
Make sure that all the pipes in the loft are lagged to prevent freezing. A couple of turns of hessian sacking is not really sufficient.
Ensure that the lid to the cold water tank is also insulated.
If you go away over Christmas, leave the heating on low to keep the house slightly warm to help prevent freezing.