I think the idea is to extend an age bracket, not to supply extra funds for the 19-25 yr olds. As it says somewhere in the link, some young people haven't quite got their act together before old cut-off age (19). Now they've got a bit more time. In this sense, it can only be considered ageist in the same way government funded education for all young people is.
Still, I do sympathise with you. Have you heard of learning loans? You borrow them from a regular bank to cover the course fees and expenses and the government pay off the interest whilst you're studying. Actually, I think they're for vocational courses only. And there's the Adult Learning Grant (£30 a week). Sorry, I know it's not much but every little helps.