The 5am HST▸ to Paddington is stabled at Worcester overnight. I have travelled on it a couple of times, in both cases there were less than 10 passengers on the train before the Oxford stop. It only became full at Reading.
Well, in my experience (I've probably caught it 30-odd times over the years) it's a hell of a lot busier than that! Granted the Worcester and Evesham stops don't get much trade - that's partly to do with the 15 minute rest the train has at Moreton-In-Marsh meaning the following train isn't too far behind and the fact that it is a new service.
Custom from Moreton onwards is far more than 10 passengers though. Typically (and this is erring on the side of caution) 15 join at Moreton, 10 at Kingham, 15 at Charlbury and 10 at Hanborough. Then around 80-100 swamp it at Oxford. Didcot Parkway varies considerably depending on whether the platform 2 departures there are running to time and Reading is also hit and miss depending on what else is around, but usually it's a case of nearly every seat taken after Reading.
