How can I remove an anti vandal tap head?
If the spanner you have is the type with a screwdriver type handle a slight rap on the top may help. Most faucet handles are made of an aluminum like potmetal. The most effective crust-buster I have found for this type of material is ammonia straight out of the bottle. Pour it over the handle and let it sit. It may help to soak a rag and leave it on top. Do this for several days (patience is a virtue) if you can, avoid using the faucet. Insert the spanner and tap it lightly with a hammer. The idea is to break up the scale between the individual threads. If you can safely do so kneel on the counter so you can add your weight to the driver to prevent it from slipping. If all else fails drill the heads off the screws. If you remove just the heads a bit of threads should remain exposed out of the stem that you can grab with pliers.