I'll be walking from the Celtic Hotel to the Embankment tube station at 5:30am in May(28th). If it rains or if it is still dark I'll want to catch the bus and will need a ticket (it will be my last day and my 7 day travel card will be used up the previous day) Are there ticket machines at all bus stops or will I need to get a ticket the day before from somewhere?
Not all the stops have machines, so you will probably want to buy the night before. Alternatively, if your travelcard is loaded on an Oyster card (rather than the paper variety) you could just load some pay as you go money on Oyster. However, isn't the Celtic hotel in Bloomsbury? If so, it is quite a bit of a walk to Embankment. There might be a better option depending on where you are heading.