Most operators provide train length information on websites, but the Class of train is less common even though I think it should be more widespread (in the same place as length, typically on the timetables) as for some operators like Southeastern or Northern/TPE it would be genuinely helpful information for customers.
I'm sure some people find unit diagrams or individual train unit allocations interesting, but I would say that's not a good enough reason why they should be provided, and I don't think they should be. Personally of course!
The FOI doesn’t really work on the basis of whether someone feels something should be provided or not. Essentially the objective is to provide info unless there’s a specific exemption in the act itself - which might be because there are safety risks arising from disclosure, or whatever. If a specific exemption doesn’t apply then info should be released as a matter of course, no exceptions, ifs or buts.
This is why Northern don’t really present themselves in the best light. Whilst it’s amusing to read their 5-page letters going to town on why they don’t want to release announcements, it’s all a bit superfluous. If they’re claiming they can’t release the info for technical or contractual reasons, then I don’t see why they feel the need to embellish this with further exemptions like labelling the requests vexatious or posing a H&S risk. It just points to a company which lacks respect for its stakeholders, which is of course a criticism often made of the public sector in general.
To use an example with my local council. I’m sure their officials don’t particularly want to release information about safety inspections they have carried out on certain trees near my house. But with no exemptions applying in the act then they have to. If public bodies were able to pick and choose what they release then it would undermine the whole concept.