Poundbury has the number 6 circular running through it every half hour,
https://www.morebus.co.uk/services/DAMY/6plus the 51 Bridport to Dorchester Sth every 2 hours.
In addition there is the number 10 service which runs from Weymouth to Mansell Square at Poundbury every 20 minutes and the Dorchester circular, number 1, running every hour, this being complete with bus tracking technology. The problem is that Mansell Square is at the entrance to Poundbury rather than the centre of it,