In reply to ThunderCat:
Walking to the west from Alston there's Grey Nag and Tom Smith's Stone top. Grey Nag is quite an interesting top with good views, although Tom Smith's Stone top is a bit of a marshy bump in the middle of many very slightly lower lumps. The return can be made by retracing your steps, heading down the Gilderdale Burn (although I have memories of hard going that way) or round over Black Fell and down the ridge on the other side of the valley. The latter is a nice route, but whether you'd do it in 4-5 hours depends on how fast you walk.
There's loads of other very remote feeling tops accessible from just east of Alston, above Nenthead, for instance. Not to everybody's taste, but I like em.
Cross Fell from Alston or Garrigill is a bit tedious. However, Bellbeaver Rigg and Viewing Hill from Garrigill is much more interesting, in a very North Pennines way.