Privatised train companies in this country have been exploiting the public for years so if having a view on the pig in the trough concept of running public transport for profit rather than as a public service is biased and negative then so be it.  The destruction of the environment by road users is growing daily and the only way to reverse that is with a publicly owned rail system run for the benefit of the public not private business.
As for ^20 fare plus ^4.20 for parking being a good deal I must have missed something or is the ^8.00 fare on the Oxford Tube a mirage?  The problem of course is that the more passengers Oxford Tube attracts the more damage is done to the environment.

I am old enough to remember when the railways were nationalised and although they were not perfect they were reasonably effective up until John Major sold them off in a manner that can not be described other than a scorched earth policy, an act of petulant vindictiveness as he saw that his Government was doomed and now, New Labour is so anti public ownership it will never do what common sense cries out for and re-nationalise rail. 
So, rather than ignoring the damage that is caused to the environment by using road transport one is obliged to do the best with what is a pretty awful industry and seek the best fare that one can.
I am now retired so I am spared the daily hell of commuting by rail and being charged an arm and a leg for doing so but I would like to travel to London now and again but I find that the car parking charges are practically as high as the car hating Oxford City Council and that is before paying over three times what it would cost to travel by bus.  However, last Sunday I read an article on finding cheaper fares, advanced fares and I thought how wonderful, that was until that was I attempted to find one for Didcot Parkway and London Paddington. 
I may not be as bright as I used to be but find an advance fare I could not and after a return of many many E-Mails with FGW^▸ (First Great Western) Customer support who appear not to know the system I am none the wiser.
Do advance fares between Didcot Parkway and London Paddington exist and if so could some kind soul please tell me how I can find them?