hi ladies, have been following this thread with interest and sympathy, my first three boys were terrible sleeps, we tried allsorts, nothing worked as such but they did all eventually sleep through, i found they all got a bit better by about 18mths, i know that will seem AGES away but there is light at the end of the tunnel!
i have thought of a few things for some of you tho
bumperlicious re the vomiting, my ds1 did the same thing, it started after he had a cough and was a nightmare he would do it every night, but we got good at telling when he was going to do it and had a bowl by the bed and would catch it in that so no changes of bedclothes or babygrows etc, we saw the gp etc and it was basically put down to the fact that coughs often make babies sick but that they can have a weak muscle at the top of their tummy? anyhow the being sick with the cough weakened it further and basically its just something that improves with age as the muscle strengthens, not helpful i know but he grew out of it by about 9mths...
re oversupply, i had this and did block feeding, you can try expressing a bit of, or just taking baby off the breast when you feel your milk about to let down and then catch the spray in a cloth and put baby on when its just dripping and not spraying out, again babies get better at coping with the fast flow as they get older.
cosmosis glad you had a better night, its fab that he can self settle so you know he will get there eventually and you said he was clingy during the day? this is common at his age 8mths? as they realise that things can go away and leave, you will notice that if he drops a toy he now looks for it, as they learn that just cos they cant see something they know its still there. but when you leave he doesnt know when or if you will come back, tis a pita, but again its a developmental phase and WILL pass, lots of cuddles and when you do leave him reassurance that you will come back and maybe keep talking to him when you walk about the room and leave the room.
all i can say to all of you is that it WILL get better honestly and dont feel it is anything you are or arent doing! i have 5 children the four boys who are now 11, 8, 6 and 3 and a 4mth old dd. out of the 5 the only one that was a good sleeper and generally still is is ds4, partly cos he sucks his thumb and could always self settle, but he has just always been good and i was AMAZED at having a baby that slept!
dd is not as bad as the first three but not as good as ds4, she has a dummy, the first of mine to have one, the first three used boob 
and tbh its good in that i can swaddle her and put her down and she generally dozes of in the pram during the day BUT if it falls out i sometimes have to put it back in, fine in the day but a pita at night, she is sleeping in our bed so its easy to stick it back in, but when its numerous times in the night......
also she will ONLY sleep swaddled and she is 20wks now! i am going to continue with it for now but once she has learned the hand co-ordination and control to put the dummy in herself when awake i may try not swaddling and start trying to teach her to put it back in, but we shall see, in the big scheme of things she does sleep, just wakes frequently at times. i half thought of getting rid of it but am a soft mummy who cant bear to hear her babies cry adn will do anything ie rock, cuddle, feed, co-sleep etc anythign so they are settled and dont cry too much! i really think we are all just meeting our babies needs by doing this and they DO grow up and dont need you so much, belieive me, soon they will be toddlers and you will wonder that they were ever so small and needy.
i do agree with routine and trying to be consistent with bedtimes i think that helps them know whats coming and merryn (my dd) def recognises nappy change, babygrow, swaddle, cuddle and then down to sleep. she was not so good a few weeks ago and required LOTS of pacing up and down and rockign of the pram to get her to sleep but has got better the last week or so, so maybe the 4mth sleep regression is passing? but tbh i think i am also better at recognising when she is tired, int he morning she needs a nap within 2hrs or so of getting up and then in the afternoon she can maybe go three hours without a nap but its best if she gets two decent long naps ie 2hrs during the day, or else she gets overtired and is a pita to settle for the evening.
anyhow i hope you dont mind me jumping in and if you have any tips on how to get her to sleep not swaddled, (she just fusses and knocks the dummy out) then i will be interested to hear them!
sorry this is so long and sorry i dont have any magic cures but i want you to know i have been where you all are and survived and gone on to do it again! 
yes i really am mad!
fingers crossed for a good night for you all xx