You could also park at the main Avebury car park and then strike out towards Silbury along the Winterbourne footpath. Waden Hill is on your left and you could take a detour to the top or carry on straight towards Silbury and then on up to West Kennet Long Barrow.

Making your way back from WKLB head for the Wagon and Horses where you can have lunch (nice garden at the back of the pub). Also at the back of the Wagon there's a footpath that will take you to the main road into Avebury. Cross the main road almost where the footpath emerges and then follow the farm road that will bring you to the Adam and Eve stones; take a right there and then a left through Avebury Trusloe and follow another farm road up towards Windmill Hill.

Coming down from Windmill Hill take a left along the road and footpath that leads back over the Winterbourne (great view of Silbury form there) into the bottom of Avebury High Street. Carry on straight up the High Street to the Red Lion - go in, ask for a couple of pints and then decide if you want to to carry on up Green Street towards the Ridgeway as Pete suggests or call it a day and have another pint and early dinner at the Lion (know what I'd do at this point).