A few years ago there was an article in "Model Engineers' Workshop" about using a cheap belt sander from LIDL as a linisher. I was in the Ilford LIDL earlier today and found that a slightly updated version is back in stock for £24.99. They are belt sanders with clamps so that they can be attached to a bench with the belt on top. I've regularly used mine since Dec 2008 having made a simple end stop which attaches to it by a tapped hole in the case. They also have cheap packs of belts of various grit sizes. A quick tip if you need a finer grade, is to run the belt on some old wood until it has worn down and then clean it by running it on a wax belt cleaning block (mine came from Screwfix or MachineMart) or a candle might do. There is an article about the original version at:
PS There were only a couple left in the Ilford store and once they are gone it's a long wait until they come back into stock. They also had a variety of other tools including air powered ones for under £30.
By the way one good thing apart from the low price about LIDL tools is the
3 year guarantee.
Alan