Thank you for your suggestions , but I have decided to cycle back down to Lochboisdale on South uist
And get the ferry to oban makes sense as I all ready have an open return train ticket from Oban to Manchester
The ferry from Lochboisdale does not go to Oban nowadays. At the insistence of one particular individual it goes to Mallaig. He thought his trucks would get further starting the mainland leg from Mallaig rather than Oban. Debatable IMO.
Before posting I did go and check the summer timetable. It is indeed as I said Lochboisdale to Mallaig.
Your best bet is to go down to Castlebay to get direct to Oban.
Mind you the run from Mallaig to Oban is not too bad as there is a cycle path of sorts alongside the A82 from Corran ferry at Ardgour to Ballachulish where you connect to another much better path to North Connel and then a back road to Oban. Do not even consider the A85 at this point.
It is also feasible to go to from Mallaig to Strontian then Lochaline and on to Mull then off again at Craignure to Oban.