I’ve just got back from a few days riding around The Outer Hebrides. We sailed to Barra from Oban (leaving the car at the Lonsdale Road car park by the Leisure Centre which is free long-stay) then rode up through the Uists and up to Harris before turning round and coming back down again.
I can hugely recommend staying at http://www.lochedge.co.uk/ A superb B+B that also does very good evening meals, has a wonderful location and very friendly owners. We also got a free, and very tasty, packed lunch for the next day due to arriving under our own steam.
The Lionacleit Guesthouse on Benbecula was also very good.
I’d also second a trip to Luskentyre beach. We camped there and it was stunning. Also make sure that you ride the Golden Road along Harris’ eastern shore as there are some simply stunning views.
Recommended cafes are the Skoon Art Cafe at Geocrab on Harris, the Temple Cafe at Northton on the south-western corner of Harris, the cafe at the Claddach Kirkibost centre on North Uist and the food at the Orasay Inn on South Uist was amazing (just don’t judge the book by the cover)
Hope that helps a bit