Introducing solids

My daughter is 19 weeks and is on the 91st percentile for growth, so she’s big and clearly loving the milk considering she was 45th percentile up until 12 weeks of age when she had a massive growth spurt. This last week she has started to sit up without support for short 20sec periods and becomes very enthusiastic when food is around or when we’re eating. Im worried that my milk isn’t enough anymore and she needs other food sources now. The NHS doesn’t recommend solids until babies are 6 months of age which is 6 weeks away... I want to do the right thing, does anyone have any advice, experience or opinions on age etc??