Thanks so much for your input, everyone!
levan, I had actually dismissed PU/PD as a bit daft - I couldn't see how it would work - but since you said it worked for you a friend of mine also said so, so I'll definitely give that a go.
PolarBear, he'll only sleep in carseat if it's moving, so that would be just as bad, really.
Beanbag, we did try a dummy but he just spits it out - he can't keep it in his mouth. Is that the same for all babies of this age, I wonder, or is DS just particularly dense at it
Nailpolish, I take your point about not wasting the baby time but he's so desperate to be asleep, he just cries and cries until he falls asleep, it really upsets him. If he was happy to be awake then I'd let him. But babies need to nap!
James&GiantBanana, I've tried the washing machine (that's how DD used to go to sleep!) and yes he is really crying. But no he's not in a routine of milk, play, nap, so that's something I could try.
RosemaryConley (LOL at your name!) now that's very interesting. I had half-wondered about getting him into the sleep time routine however I could and then adjust the sleep place - but I'd talked myself out of it as I decided it would just prolong the problem. But that's great to know it worked for you, that makes me feel more optimistic! I think it would be pretty hard to do this with a school-age DD but maybe during the Easter holidays when there is no school run to worry about. Also good to know that your DS just learned to fall asleep by himself - how old is he? (please don't tell me he's 8 ) I think that's what I'm most worried about - reinforcing the problem. If someone could guarantee me that he would learn to sleep by himself when he's older, and that I wouldn't be pushing that back, then I wouldn't be so stressed about it. I could also deal with it better if it were spring - the daily 2 hour walks in the rain are getting veeeeeery tiresome
Thank you so much everybody, I really appreciate your thoughts and advice!