Been based in SG the last few years - in the process of moving back to Aus now.
Unless you're travelling back to Aus (or onto LHR), I'm not sure that QFF is worth it. There's opportunities to earn on 3K, but lounges are pretty rare, and there's no status perks on 3K.
If you're flying J/F, then SQ has PPS, which is worth getting. Otherwise you can look at other *A partners to get *G (rather than SQ), and get lounge access quicker than via SQ's program.
IMHO, CC aren't particularly good value in Singapore (well, no better than Aus). For earning points there's Citibank PremierMiles and DBS Altitude Amex (and now Visa IIRC). HSBC has a Visa Infinite card which may be worth getting for the car transfers to/from the airport, plus Jet Quay (CIP) lounge access. Note that CC protection in SG is quite a bit less than in Aus (e.g. from what I've heard charge backs can be a real PITA to organise). The only airline partners that I know of in SG are SQ, TG and CX. No card transfers to anyone else.