If they are, it is simply a case of using your slotted screwdriver to turn the centre screw to the horizontal position, as shown. The water supply will now be isolated, and you can safely continue work.
If there are no isolation valves present, you will need to turn off the water supply to your entire home. This is achieved by first locating the stop cock:
Most stop cocks are located under the kitchen sink, however in older houses they can be in a variety of places; search by your front door, in metre cupboards, in cellars, even in old outside toilet buildings. Turn the stop cock spindle clockwise until tight (do not over tighten). This will isolate the cold water supply to the entire property, and may also (depending on what type of installation is present) isolate the hot water supply. If the hot water does not stop running, this is most likely because your home has a hot water storage cylinder:
Hot water cylinders are normally found in an airing cupboard. When changing taps where there is stored hot water, it is vital that you turn off the hot water and allow it to cool before continuing work. Once you have done this, locate the gate valve which feeds the hot water. cylinder:
As with the stop cock, turn the spindle clock wise until tight, this will slow down (but not completely shut off) the hot water.
STEP 2.
Now that both water supplies are isolated, open up the taps on either the bath or downstairs sink, this will relieve most of the remaining water pressure, although there will still be a small amount of water in the pipes and taps when you remove them.
STEP 3.
You are now ready to remove the old taps from the basin. Using your tap spanner, latch onto the fitting that joins the pipe to the tail of the pipe (this is normally brass, but may be chrome or plastic) and turn it anti-clockwise. You may need to hold the tap in place to prevent it turning whilst undoing the tap connector. It is worth noting that the current taps may have been on for literally decades and may be extremely tight. In these instances, spraying WD40 on the threads of the taps may help. Remember, there will still be some water in the pipes and taps, especially where you have used a gate valves to isolate the hot water, so DO NOT PANIC, but keep an old towel around the bottom of the basin pipes to keep mess to a minimum.