I started introducing solids when DS was 5.5 months corrected, 8 months actual age. I live in Germany and here the advice is to begin weaning between four and six months for all term babies, and between four and six months corrected age for prem babies. I know the advice in the UK is not to use the corrected age, but I don't find the reasons given at all convincing: so what if the gut starts maturing at birth? Why do babies that are ebf for much longer than 8 months, as is the case in some indigenous peoples, do not have more problems regarding allergies, nutrient deficiencies etc.? And how can a baby that is 2.5 months corrected age ever assume enough solids to make up for a nutrient deficiency?
Milk is the main source of food in the first year, and I cannot imagine why a prem baby should be fed solids when it is still so tiny - DS would never, ever have been ready for solids at 5 months actual age, when he should have been just 2.5 months old.
Prem babies are definitely at a risk of a lack of nutrients, but IMO it makes more sense to give a supplement instead of hoping the few spoonfuls of solids your prem baby will eat a few weeks after its due date will give it enough of the nutrients it needs/is lacking. I give DS Wellkid liquid, he is now 8 months corrected and has only just started enjoying eating solids.