I go with the advice to try to sleep mainly on the second leg, although in the past I have found that if I sleep for an hour, or an hour and a half, on the first leg after a reasonable meal and wine, it doesn't affect sleeping on the second leg, but gives me that little more sleep. I agree with the singapore shower (fantastic curved shower room in F lounge) . I have also slept for a couple of hours in the morning on arrival, but I live within 25 minutes of LHR, which makes that easier.