I don't think it's done in these days of almost universal washing machine ownership.
Flat items such as bedlinen were put in a pillowcase and left to be collected by the bagwash people. They'd wash it, dry it, fold it and return it. It was far cheaper than a laundry, which would wash any item and iron it, although I suppose it was washed in the same machine. For beds it was a perfectly satisfactory solution for poor people who'd otherwise have to heat water, wash by hand, hand wring and dry in the street or round the fire, taking up precious room in a very small house.
Your cheap housing in Harrogate was blessed with hot water - but I imagine that it was more recently than when we lived in our little house.
Mary