There are 25 direct and indirect flights connecting Southampton and Singapore every week, with the journey taking 21 hrs 45 mins on average.
Or, if you're fairly flexible on dates, try to get a last minute-deal by regularly checking the Netflights website.
Singapore actually has one airports to choose from – but Singapore Changi International Airport (SIN) is the usually the cheapest option. If you need to fly into a specific airport, adjust your search to focus on those flights. The most popular airlines include British Airways.
But if you can't find one which is right for you, try looking at flights to other cities in Singapore to check out some other options.