my 2 cents worth:
with 2 young children... long haul flights like singapore london can be very challenging...
with oasis/jetstar... can be a nightmare since many of the "perks" will not be there...
direct flights are more expensive (BA/SIA/QUANTAS/Virgin Atlantic)
but i think the hassle of waiting and going thru customs again after a stop-over can cause you to swing the way of a direct flight...
On the other hand, if your wife and you can afford/dun mind taking a single stop over... then Thai airways, MAS, Emirates, Qatar airlines will prove to be very competitive options indeed...
All in all, if it's your 1st time taking such a long flight to a foreign place, i would recommend going with SIA or some other reputable airlines so as to lighten your stress and load on the flight itself (I just got down from a london-> sg flight sitting next to a naughty and noisy 5 yr old) you would be amazed at how much difference a well-trained flight attendant will make to your trip... to me, saving that few hundred dollars between MAS and SIA isn't really worth it... but if cost is the most impt aspect of your decision making, then a good compromise would be single stop over...
Hope that i have helped u a little bit... cheers! enjoy ur time in UK!
