Libby, you might have a Fit for Life council run free class near you? There are several here in London. Some are way tooooo slow, for very elderly or sick people. I go to a nordic walking class. We nordic wal...ahem... stroll around a park (flat, bit boring) but the people are so nice and afterwards we end up in the park's coffee shop, undoing all the good we did a short while earlier. But it's nice to get out and walk and the teacher's great. She brings the poles for us all.
nordic walking is great as it gets the arm muscles moving too, however many of the official nordic walking classes aren't free, if that matters to you.