Thanks for the advice everyone, and it's nice to know I'm not the only one having trouble! I will try and settle him for his naps sooner, and perhaps feed every 3.5 hours and see what happens. Sadly, today was not the day to start anything, as had early doctor's appointment which has sent everything to pot.
Only problem with earlier naps, is sometimes he just doesn't seem tired or show any sleep cues. Yesterday for example, I got him up at 3 for a feed. As it was sunny, i took him for a walk in the pram afterwards and, unusually, he was wide awake and interested for the whole thing. When we got back, it was 5.00. I sat with him on the sofa - he was happy and didn't seem in the least bit tired, but as he'd been awake for over 2 hours, I thought it was best to try to put him down. Well, that didn't work, he struggled and cried, and in the end I gave up and took him back downstairs. Later on he fell asleep for fifteen minutes in his chair, but woke up himself. At 6.30 we gave him his bath, then a feed at 7.00. He was wide awake at the end of the feed, but I took him to the bedroom, tried to wind him down and put him to sleep, but he just didn't want to go. After over an hour in the nursery, my husband took over for half an hour. By 9.00 we hadn't eaten dinner, and he was still awake and unhappy, so in the end we took him downstairs and put him in his chair so we could eat. He sat there quite happy and again, wide awake and didn't even yawn or show any signs of tiredness until about 10.00. I gave him his dreamfeed during which he fell asleep only to wake up again the minute he touched his cot. I got him settled after fifteen minutes or so and eventually, after expressing, went to bed about 12.30. He woke for a feed about 3am and went down relatively easy afterwards - and then woke again at 5.30! He showed no signs of hunger (even when I eventually fed him at 7.00, he wasn't interested until he started feeding) and I couldn't see any other problems. Either way, I spent an hour and a half trying and failing to settle him, eventually lying on the floor in the nursery. When I gave up and took him out of the nursery to feed at 7, I could see that he was wide awake, and can only assume that he wouldn't settle purely because he wasn't at all sleepy. After yet another night of no more than 4 and a half hours sleep, I'm at my wit's end! Should I still be putting him to sleep if he isn't acting at all tired? Any tips for getting him to sleep other than dummies, swaddling, music, dark room, holding him etc, all of which I'm trying! And how long should I sit in the nursery trying to get him to sleep when he's so obviously resisting? Should I take him away and try again later?