Many people have a phobia about spiders, but in the UK we are lucky as the common house spiders and ones you may see running about are not usual harmful to us. Spiders can bite and if you get bitten by a spider in the UK it is rare, but you could have a reaction to the bite. Usually this is very easily treated and you will not require urgent medical attention.
If you chose to holiday in Australis you should be aware of the many types of spiders that can cause serious illness if you are bitten and sometimes even prove fatal. One of the common spiders to Australia is the Black Widow spider. These spiders are considered dangerous because of the  neurotoxin latrotoxin, which causes the condition latrodectism that they pass on when you are bitten by one. They tend to lurk in such places as the toilet bowl or letterboxes meaning that you must be very vigilant and make sure that you check places first before sitting or putting your hand in.