Baby isn't taking to lumps too well.

How are your babies getting on with weaning? I started weaning my son at 5 months and he's 6 1/2 months now so now I need to start adding more texture. He's not very keen on lumps and sometimes he just won't open his mouth and blows raspberries. He was eating well he was on 3 meals a day and now I'm struggling to get him to eat. He had stopped nightfeeds for few weeks and now he's taking less during day and feeding during night. I'm starting to find weaning stressful. I'm from the UK and we are advised babies should take 18oz of formula daily now (or breast milk) and be on 3 meals. My main concern is if he doesn't progress to lumps soon how am I going to get him off purées? I've tried the baby led weaning also by offering bits of food but he's not interested and just squashes the food and throws it. It doesn't go into his mouth. Am I expecting too much of him at 6 months? Lots of people tell me their babies sleep through the night and eat well and I don't know what I'm doing wrong.