Hi Ianbotham
I will give you an honest assessment of Chennai from a foreigner's perspective. I lived and worked in Chennai for over a year, beginning in 2010.
Chennai is extremely hot and humid ALL of the time.
Chennai, is not modern at all, unless you consider having a few McDonald's restaurants, KFC, and a select few other American style places modern. As was stated before the people are not very friendly to foreigners (however your co-workers could prove to be otherwise), they are extremely nosy, asking all sorts of personal questions,and very judgmental. You will most likely find it difficult to get adequate housing at a reasonable price if this is a consideration, unless your company is paying. There are frequent and scheduled power cuts, so you must have an inverter otherwise you could be without power for hours. Contrary to what most people think, it is not cheap. If you want to get a similar standard of accommodations to what you might be used to in HK, you will definitely benefit from the size as compare to HK, the apartments and houses in Chennai are much larger. However you will be looking at close to or over Rs100,000 per month plus utilities for a modern, well located (either in Mylapore, Alwerpet or on the East Coast Road) or close to your office so you will not have an extensive morning commute.
You MUST have a driver, the traffic is horrible, it is very dirty and dusty and the roads do not have any proper markings. There is virtually no public transit, with the exception of Tuk Tuk's and city buses (AC and non-AC), they are currently building a metro line which only ads to the traffic congestion and dirtiness.
It is very conservative! Rarely (compared to Mumbai & Delhi) will you see other foreigners, most women still wear traditional sari's, even throughout the workplace and in all types of roles, even doctors, lawyers, etc. It is NOT the safest city in India. It is a very largely populated city, which is growing every day and becoming more and more expensive thus contributing to the increasing crime rate as well. However overall it is a safe place to live.
Other things to consider in your job offer:
-Taxes - you will be subject to a minimum tax rate of about 30%, so you must deduct this from your salary and see if it still looks great
-Moving costs, will you want to move your belongings from HK? If so, who pays? And also it is a nightmare getting it thru the port unless you are prepared to bride a lot of officials, as I had to do. And would therefore recommend you get your employer to deal with this and have all your stuff shipped direct to your new home as this will save you countless headaches.
-Does your job offer include a car/driver? Or will they give you a budget for this? It is very normal in any management positions to have this included? Or at least a driver. This is an additional cost of at least Rs7500/month and cars are quite expensive as well. Not sure what they cost in HK, but compared to North America, I found them expensive. As is fuel.
-How/when will you get paid? I found it quite challenging to get paid in Chennai, unlike North America it is quite common for employers to NOT pay you on the 30th of the month, but rather around the 5th or 7th of the following month. This I found quite appalling and made it difficult to budget.
-Again, I cannot say enough about the difficulty in renting in Chennai. On top of the costs, most apartments/houses unless they say they are fully furnished do NOT come with appliances. Again very different than North America. And more shocking is most landlords will demand a 10 months deposit in advance plus you will have to pay the monthly rent and then try to get your deposit back (without interest) at the end of your 11 month lease. This should also be negotiated into your contract.
Hope this helps.