The path from Sparsholt Firs starts easily enough but then drops downhill and becomes very rutted. Cross the minor (but fast) road at Blowingstone Hill with care. This is an alternative starting point with some car parking. The track is ok for a while before becoming rutted again. Keep over on the left hand side (going west) to avoid getting stuck.
Leave the Ridgeway to visit Uffington Castle (Iron-Age fort, earth ring) which makes a pleasant lunch spot. The White Horse is not visible from this route.
Alternative start point at the car park at Woolstone Hill, White Horse Hill