My dad's neighbour had Bulbar Palsy, a nasty variant of MND. Its only saving grace is that it usually relatively quick (short years/months rather than many years). You progressively lose the ability to swallow and talk (it was in fact her speech that Dad - a retired medic - noticed and suspected Bulbar Palsy really early on but didn't tell her himself until it was officially diagnosed).
She had brilliant palliative care but ended up making the decision to stop allowing herself to be peg fed, so that she had control over her death. She stopped eating on 31 December (which she'd announce about a month before) and, iirc, lasted another 2 or 3 weeks into January. She died at home with her husband, son and daughter-in-law by her side. They were all devastated but respected her decision. The carers helped ease the final days.
MND is a horrible, horrible disease 
My dad had a Swiss fund - although at least in Scotland, relatives/friends can accompany someone going to Dignitas and not worry about potential prosecution on their return.
In the event, he died suddenly and unexpectedly so we never got to that situation.
He had signed the petition asking for assisted dying, with safeguards, to be legalised.