Epic post, apologies in advance!
My DS is 4 months (coming up to 19 weeks) and last weekend we returned to Singapore where we live atm after 3 weeks holiday in the UK and I'm finding it difficult to get him back on this timezone which is 7 hrs ahead. I'm aware this timing coincides with potential sleep regression anyway so hard to tell if it's just jetlag at work.
I know I need to work on improving his sleep in general (naps and night time) but the more urgent concern is helping him to recover from the trip.
What he was doing most nights and adapted fine when we went away (east-west easier than the other way...) was 4 or 5 hours in the Sleepyhead in sidecar cot or travel cot from quite a late bedtime around 10pm. I want to get him on a more appropriate bedtime but thought there was little point in trying to change things until he was back on this timezone. He's pretty much always BF to sleep at night then from first wake up 2/3am I would BF lying down and generally sleep myself. Sometimes I would wake a bit later and plonk him back in sleepyhead other times we would co sleep for the rest of the night and he would feed every couple of hours until up for the day around 8 usually.
Now it takes longer to get him to sleep then he will wake after 40-60 minutes and often be wide awake / chatting or fractious and even more difficult to settle back down the next time and frequent wake ups all night. I have taken to co-sleeping earlier on as the 4/5 stretch is not happening which helps him settle initially but he still wakes to feed every hour or so with maybe a 3 hour stretch in the early hours. A bit vague on exact timings as I'm half asleep myself!
I read you should allow a day per hour time difference and have tried to bring his bedtime forward an hour every day but he doesn't seem to be adapting 
. Last night gave him a bath at 8, fed him, got him to sleep after about an hour (in the sleepyhead), he slept for an hour then up again and not back asleep until 12ish after feeding, cuddling etc. Ended up sleeping in this morning as so tired but I don't know when up time should be since his night sleep is so poor.
He's not particularly napping more during the day and since he stopped reliably napping after feeding I have made more of an effort to rock him in the pram / bouncy chair once he's been awake coming up for 2 hours. I've been trying to offer BF every 2 hours during the day to tank him up but this isn't always successful as he's in that majorly distracted stage and finds almost everything else more interesting than concentrating on feeding. And no wonder considering he's munching all night! For example I left a bottle of expressed milk with DH this morning while I went out and he didn't drink any of it although several hours since his last feed (though in fairness DH is used to DS screaming for milk so probably didn't think to offer it if he was content).
I've been reading the No Cry Sleep Solution but it seems pointless making a grand sleep plan when his body clock is still so skewy.
I suppose my (long winded) question is should I just do whatever I can to get him to sleep for now and worry about getting him to sleep alone for longer stretches later on? What can I do to help him? What time should I try to put him down for the night and when should I get him up? I feel so bad that he is all confused and sleep deprived due to us going away (although on the plus side he got lots of grandparent cuddles 
).