Stopping distances increase on wet roads so you should always leave more space between your vehicle and the one in front.
Use your wipers to give you the best possible view out and don't use your full beam headlights unless it's absolutely necessary to give other drivers the best chance of seeing you. The same goes for rear fog lights, don't use them unless it's foggy as they can mask your brake lights and stop other drivers realising you're slowing down.
Also take extra care when overtaking other vehicles, particularly HGVs which tent to kick-up a lot of spray. Be on the lookout for puddles and standing water at the roadside. Driving through it too quickly can reduce your visibility and that of other vehicles.
In extreme case it can also lead to aquaplaning. This is where water breaks the contact between your car's tyres and the road. If your steering goes light while driving through water, don;t brake or steer, just ease off the accelerator and wait until you've passed through the water before you try to brake or steer again.
Extremely heavy or prolonged rain will inevitably lead to flooding and a whole new set of problems for the intrepid UK motorist. The basic rule with a flooded road is simple: never drive into water if you're unsure of its depth.
Be doubly careful if the water is flowing, even slowly moving water can lift a car and carry it away.
If you do decide to try and cross a flooded section of road there are a few things you can do to maximise your chances of getting across safely. Firstly, stick to the highest part of the road, which is usually the middle because of the camber designed to help drainage. Getting your speed right is important too, you need to drive slowly but steadily, not so slow that you risk coming to a standstill but not so fast that a bow wave is created which might engulf other vehicles or your own.
Keep your distance from the car in front, if possible allow the vehicle ahead to reach the other side before you enter the flood water. That way you can gauge if it's possible to cross safely and avoid getting stuck behind another car that comes to a halt in the water.
Once you've passed through the water, always test your brakes to ensure they're still functioning correctly and if your car becomes stuck in deep water don't attempt to restart the engine or you'll risk turning a big repair bill into a huge one.
Wait for the car to dry out and get a professional inspection before trying to drive it.