Hi there Simon,
I don't know much about Perth but having been in Sydney 4 months now on a similar income 'swap' to yours (£46k to $150k), I would say you will have a better standard of living than you currently have. Obviously I can only speak from our situation, others may be different, but so far we are finding life here more comfortable than life was in the UK....and we live in Sydney! We are shelling out quite a bit on rent each month,but for that we are in a 4 bed place in a good suburb only 30 mins from the CBD (in the UK we were in a small 3 bed house miles from a decent town). Cost of living wise, some things are cheaper (coffees, petrol, shoes), some things not (clothes, branded goods in the supermarkets - cereals etc). One problem you might find here though is if you want to buy a house in the future....our money left over from our house sale in the UK last year is still in the UK and with the exchange rate will not be as much in AUD as we need for a deposit here on a family sized house. Anyway, hope that helps!