Some parts of the UK would automatically add this to the end of sentences, when conversing with others. You would be more likely to hear this in parts of Lancashire/Yorkshire. Around Newcastle they would often add "pet" to the end of sentences and in Northamptonshire they often add "duck". for example "How are you, pet? You would only ever come across this in spoken English. It is considered to be familiar language so people who consider themselves to be "posh" would not say any of these things.

It is a familiar form of address in Britain which can also be used by women, for example by an older lady towards a young person (boy or girl), but most of the time by a certain type of man towards women. While not really offensive, it would certainly be regarded as over familiar in polite society, if one were to use it to address a person whom one is meeting for the first time.

Anne is right although this would not be commonly used In the northern parts of the uk mainly a man might say alright love. however a large part of the country would consider this strange and certainly not polite.

Some decades ago it was common enough in Australia, but now it's considered a little condescending.

I would certainly not say that and it would definitely sound odd to me. However, I can certainly imagine there are some places and/or people who would say this in a totally innocent way. If an older man said it to a younger woman I could see it being a substitute for "dear" or "young lady" or something equivalent.