In reply to Hammy78:
Going N-S does head in to the prevailing winds ... However the last time I was out there we went S-N and had a northerly for the entire time
Train to Garve then bike over to Ullapool? The usual complaint from bus/coach drivers about carrying bikes is that they don't want to handle them in case they cause damage to the bike - I've just said that it's fine and I'll put the bike on/off the bus and am happy for it to be loose in the baggage storage.
Allow a day to get to Ullapool possibly getting a late ferry over to Stornoway.
A day to get down to Leverburgh. Getting to Berneray is by ferry and one or two sailings are affected by low tide so worth checking this out.
A day to travel down through the isles, not looked at ferry times from Castlebay so not sure if you need to get there early in the AM or not. This is quite a long day, especially if there's a head wind, but is flat apart from a couple of small hills.
Don't you have to go Castlebay - Oban then Oban - Tiree?