Here is the first draft of my proposed letter to Northern Rail, I have taken the liberty of using some of the useful points made by other contributors on this thread. Have I missed anything out etc ?
I found out today that I was unable to buy a ticket on the train from Chapeltown with our family railcard. The guard told me it is a penalty fare route and though there may not be a ticket office there is a ticket machine so I must buy my ticket before boarding, or at least get a "permit to travel" and then buy my ticket on the train. This was the first time I had heard of this as we only travel from Chapeltown every few months, I have always bought my tickets on the train when travelling and we have never had a problem before. I cannot say I was impressed with the guard's attitude as it was obvious we were not trying to avoid paying, and in fact we did so using our railcard by getting off at Barnsley and using the ticket office there.
We always travel north from Chapeltown station as we park on the road west of the station then walk down the path from the north end of the station. But Chapeltown only has one ticket machine, which we have never even seen because it is on the extreme end of the other (southbound) platform and hidden inside the shelter. At Chapeltown getting to the ticket machine involves quite a trek right to the end of the P/F, down a long flight of stairs, round the road, then up another long flight of stairs, then all the way back again to catch the train. Obviously that is incredibly inconvenient and also requires getting to the station earlier, plus having to add on contingency time just in case there was a queue for the solitary machine, making it even more inconvenient.
However, that is for someone able bodied, what about those with mobility issues ? How are they to access the ticket machine and then back onto their platform ? The advertised "step free access" requires a very long detour (and back again don't forget) including having to walk the entire length of a busy Asda car park with no segregated footpath. Thus I would argue Northern Trains are in breach of the Equality Act 2010.
Leaving specific disability issues aside, Chapeltown is effectively two stations (up and down) as it is not possible, even for the able bodied, to get from one platform to the other without exiting the station and walking along the public highway, and therefore, if travelling north I effectively do not have the opportunity to buy a ticket and therefore your penalty fare conditions are invalid.