I read that earlier ally - it is very unfair that people with disabilities even have to book assistance at all
And borderline unlawful ... I don't consider it a "reasonable adjustment" (except when people mistakenly say "reasonable" instead of "cheapest possible - and even then we'll begrudge that.").
Able-bodied people can book seats online 24/7. Start becoming a nuisance, and it has to be a phone booking.
If I had time, it would be interesting to see if theres a FOI path to get the train companies to release the assessments they made under the DDA and work out what %age of their passengers are disabled and see how that squares with the %age of seats they offer.
If the UK were serious about disability rights, it would also become a slam-dunk criminal offence to abuse a facility provided under the DDA.