What are the advantages and disadvantages of doing a postdoc in Singapore and UK?
My answer will focus on entirely non-academic aspects of a post-doc in UK as you seem to have those "sorted".
I think you have been slightly mislead:
- ~£30K will not result to ~£18K after taxes. I was taking ~£31K and ending up with ~£24K. Maybe you are in a different tax-category or something but from ~£30K to end up <£20K is quite unrealistic. Finally, ~£30K with 0 years of experience is pretty decent. One more point: spend an hour or two and check the HM Revenue & Customs. Do not rely on word of mouth on something so vital.
- You need to factor council taxes and these will dependent where you live. Council taxes can be quite hefty (£100+ per month in Cambridge for example).
- As @John mentioned, you need to base your decision on where are you going to live; ~£30K in central London, Oxford or Cambridge with 2 kids? No way. ~£30K in Manchester or (even cheaper) Coventry? Probably tight but doable.
- London allowance have not saved anyone. Sure you will get probably ~12% more than your equivalent post-doc outside London but that's about it. In some cases you can get the same salary outside London. Lesser known universities try to give more monetary incentives to candidates.
I recommend you do some very good research about where exactly you are going, what is the cost of living, what are schools/nurseries are there, etc. Also do maybe a quick online search for houses to see what is available. If the going rate of a two bedroom flat +£1100 well... you need to consider things seriously. And do the same search for Singapore too afterwards!
Post-doc is a stepping stone. Realistically you will not get a salary that will allow you to live a luxurious life. Also take into account that the chances of tenure in an institution after a post-doc while usually better than being a complete outsider are all but guaranteed. Therefore consider that relocation might be something you will have to re-examine. You do not tell us if your wife will be able to contribute to your family income. Even a part-time job might make a significant difference.
(Reading back my answer I think I sound a bit grim... I do not mean to dishearten you or anything, just I do not want to be mislead on taxation or living costs issues.)
To put the following into context, I teach at a UK university and have delivered courses at a Singapore partner university for many years.
In support of many of the above comments, you need have no concerns about the academic establishment in Singapore, at any level, from primary through to university. Education is top of Singapore's agenda and this is apparent everywhere. Teaching is in english throughout. Singapore's universities are world-class.
The living and working environments are excellent. Cost of living (apart from housing) is lower than UK. The transport system is also excellent.
Cost of accommodation is the only negative. Apartment rental costs are high - comparable to London. However, if you are appointed on expat terms the University will provide an apartment and the rent will be subsidised; all large companies that employ expat staff take account of accommodation costs. But you should make sure that you know what type of apartment is on offer and that it meets your family needs. 'Landed properties' form a very small part of Singapore's accommodation, the large majority are high-rise apartments.
Income tax is much lower than UK levels - you can check this out on the government's IRAS web page.
It is typical that you will disproportionately get speaking invitations from, and make connections with other researchers, who live near wherever you do your postdoc.
For these and related reasons (e.g., employers knowing and trusting the people who will write letters for you), one advantage of doing a postdoc in Singapore/UK, respectively, is that it makes it easier to get a permanent job in that respective part of the world. So I would recommend thinking about your long-term job (and family life) prospects in the UK and in Singapore respectively.