We were in the Outer Hebrides in June, hoping to get out to St. Kilda, but the weather prevented us. Instead, we wore our way down from Harris, through North and South Uist to Barra, mostly camping, and with some good walks.
The only “mountain” climb was Heaval, Barra’s hugest summit at 383m. A quick steep climb from the high point of the road east of Castelbay, up past the Madonna statue. Great views in all directions, although hazy.