my LO seems to not want to eat at lunchtime at home- ok at nursery?
Are you eating with him at home?
I think sometimes at groups or nursery they see everyone else sitting for their food, and eating, and it encourages them to eat. Humans tend to be social eaters, we eat more when other people are eating with us.
I agree with LT that cues for lunch time are helpful (cues for anything give them a chance to prepare for it). And moving times can help too. We still have a pretty 'odd' meal time at around 3pm because this is when DS tends to be at his hungriest. It's our 'big' meal of the day where as the earlier lunch around 11.30/12.00 is sometimes more snack based while we are out and his later meal at 6.15 he sometimes eats loads other times not so much.