If you think about it, needing a solicitor's letter makes sense, as otherwise everyone would be claiming their parents were divorced and thus getting loans and grants they weren't entitled to. The system is open to abuse in so many ways that it's good they've closed (or made harder) that one!
Yes, it's annoying for you, but I'm sure you'd find it annoying if everyone claimed too much so they had to lower the loans and grants drastically to cover the people claiming fraudulently!
Yes, legal aid still exists. Or some solicitors offer one hour free, but they might charge around £25 for a letter.