Couple of other ‘developments’ that might improve the Avebury WHS.
1) Tarmacking the main NT car park which, at 5 quid a bash, is definitely warranted (though there may be legitimate objections from the archeo community to doing that). Tarmacking would certainly allow better wheelchair access from there to the High Street though.
Alternatively, 2) allowing disabled parking at either the Avebury & District Clubhouse car park, or the small NT car park in front of the Hengeshop.