I think there's a couple of key points here:
Training
Training for frontline roles on the railway is generally done in a very structured way, as it's a legal requirement that rail businesses have procedures in place for provision of training of their staff. Quite often due to the turnover of staff, frontline staff are trained in groups, so it isn't feasible for each new recruit to be individually reviewed to see how much training each will need. Therefore there isn't a benefit to the TOC in such roles for taking on people who already have some knowledge, though if you do already have a background knowledge, I would expect that you would find the training easier - but that isn't going to help you get to that stage.
Application
Generally railway job adverts tend to be well structured and in the advert it will give an indication of the sorts of skills that the company is looking for. Generally for frontline roles they'll include things like customer service, following safety rules, ability to do shift work, possibly cash handling, manual handling, COSHH, lone working etc. When they're shortlisting applications, these are the criteria they'll be shortlisting on - managers will often get tens, possibly even hundreds of applications for a given role so it's important that it's clear in your application how your experience relates to these competency areas that they've asked to see.
That said...
My own view is that as an industry we don't always get the best people because it's all very bogged down in 'previous experience' and 'competency based questions' and whatnot rather than the soft skills and individual characteristics. To get a job as say, station staff, you have to be good at writing an application, and answering competency based questions (the latter where if someone's good at answering the question then they're going to most likely be good at embellishing an answer or, indeed, completely making it up), but there's no guarantee at the end of it all that that person who's good at those things will have a positive attitude towards work, or the soft skills for helping confused customers or controlling aggressive ones.
I think as an industry we have many jobs where you don't really need experience, just a reasonable standard of education, a good demeanour with people and a willingness to put in the effort and work, but we don't 'home-grow' that talent, when that provides a great opportunity to develop people for a career in rail at a time when actually, in many areas, it really is a struggle to recruit.
My suggestion...
...would be to do what you can to get some additional experience under your belt in relevant areas. Volunteering at a charity shop you might develop skills in cash handling and customer service, volunteering at a heritage railway you might develop skills in working to safety procedures and helping disabled visitors. Jobs in restaurants would give you food hygiene experience (useful for onboard catering roles, for instance) or working in a bar would help you develop skills for dealing with difficult (eg, drunk) customers. The more good experience you can get to tick more of those initial boxes, will put you in a better position for applying. Also, keep an eye out as some rail businesses are starting to do apprenticeship programmes, which are a step in the right direction for those with less experience.
