I think a lot of people here are overcomplicating things. Really, all that needs to happen is two things:
- A programme to bring platforms to the existing UK platform standard (915mm), and provide level access to these platforms (via e.g. ramps, lifts depending on situation)
- All new rolling stock should be required to offer level boarding with gap fillers, as classes 231,745,755,756,777 already do. At least 3 manufacturers (Stadler, CAF, Siemens) are capable of delivering this, and the rest could do it for future designs. All manufacturers in mainland Europe offer this, it.
Automatic ramps aren't going to be retrofitted to existing stock anyway, and for new stock going straight for level boarding makes more sense, as it benefits everyone, people with mobility needs, people with baby strollers, people with a lot of luggage, etc.