Are all new washing machines the same size?

The majority of UK washing machines are roughly 850mm high, and 595 - 600mm wide. They can vary much more on depth though, which is usually less critical because a washing machine that's deeper than average will still fit in the space, it will just stick out a bit more. Most budget and mid-priced washing machines should be the same dimensions give or take a few millimetres. Most UK households install a washing machine under a work surface in a fitted kitchen. If a washing machine's size deviates from the standard size then they will lose sales. More expensive, quality machines are aimed more at the kind of people who have separate laundry rooms. If one of these washing machines is slightly bigger, it won't matter because they will normally be free standing.
Always check the measurements, especially if the space available for it is not generous. Don't overlook the depth of a new washing machine, which can cause problems in kitchens where a door or drawer opens just in front of the washer. The main things to watch for are control panels, buttons, doors and control knobs that stick out much more than your previous machine did, which may prevent a drawer from sliding out, or a cupboard door from opening.