Weaning advice? so varied 😐

Ra
In the U.K. we are told not to wean until 6 months. I feel my 18 week old baby is needing weaned he is a big baby. At my weaning visit she advised he could start stage 1 weaning (baby rice, veg and fruit). I've been giving him baby rice in the evening and I am going to start a second meal. I would like to start porridge for breakfast but don't know if would be better starting veg for lunch. Some books tell you no cereals until 6 months but is porridge a cereal. 
I'm finding everyone's views all contradict each other. Advice from parents leads to disagreements because it's "changed since their days". But then did it really do other babies harm being weaned at 4 months. Is our poor diet and availability of fast food to blame.