Well, I lived in Kensington. I have to say the accommodation cost here is probably similar to the UK (judging from the letting income we get from renting out our flat in Kensington). Do not expect the finish or size of the apartment here to be as good as London.
I would definitely come here to visit even just for a few days. It will be worth it to see what it’s like. My husband hated it at first and if they didn’t pay him so much, he wouldn't be here after 4 months.
Consider your wife lifestyle also. If she’s used to have her own career back in the UK, she might be frustrated here and feel worthless sometime (like me). After 4 months, Hong Kong is a small place to live. I would come here with your wife, if I were you. And try to imagine what's it like to live here. To put it lightly, they have a different standard of manners here. I am saying this in a very factual way, not at all racist or snobbish way. Their manners can annoy you on the daily basis to the point that no amount of money can compensate that.
On the bright side, it is cheaper to eat out (not sure about the quality of food though) and to shop. Again they have either the top range brands or the street market no-brand, not a lot of in between such as Gap, Top Shop.
Hygiene will become almost your daily concern, unlike when you live in London. You think about it in the MTR, on the street, supermarket etc. I also find supermarket food packaging here is not very good. On some day I find that I get an upset stomach from eating food from the local supermarket. The more international supermarkets mark up the price to about the same as the UK, so not a lot of saving there.
I'm not sure whether it is better to be here if you already have a good life in the UK. But if you think you will come here only for a couple of years to advanced your career and go back, then it should be alright.
Oh, if you wear contact lens, be preparing not to be able to wear them in Hong Kong and prepare a nice pair of glasses to wear. Your eyes will become dry to the point hat you may not be able wear contact lens for a long while.
I know it sounds really negative here but I think it is something you need to consider before moving here. You might not mind what I mentioned above at all.
It’s more fun to be in Hong Kong than the UK. It’s more civilised to be in the UK than Hong Kong. English are more open minded than Hong Konger. Professionals are more professional in the UK. You can trust that your employer will not do anything which against human rights or employee’s rights in the UK which is quite a reassuring thing. It’s quite a lonely place to be here if you just can not get along well with your colleagues. One more thing, from the people I know here and my husband’s company, be prepared to be the white western minority in your company. You will feel like an outsider.