You HAVE to use the right words to describe what you are doing. In your day job you must encounter the same problem (ordering new clutch plates when you meant brake pads is going to be expensive).
Clues about your washing machine socket being a spur or not.
1) How many wires are in it? Only 1 wire of each colour (red, black and earth or brown, blue and earth) would indicate it is not part of a ring final circuit. More than 1 wire of each colour might indicate RFC or might be a spur of a spur.
2) Which fuse (or MCB) at your consumer unit controls the washing machine socket? Does that fuse/MCB/RCBO control any other sockets or appliances? How many live wires (red or brown) go into that fuse carrier? Is the fuse carrier red or blue? (or is the MCB/RCBO rated at 32A or 20A)? If the carrier is RED (or 32A MCB) then you'd expect to see 2 live conductors connected and that circuit is probably an RFC. If the carrier is BLUE (20A MCB) then the circuit is most likely a radial- be warned, there could be more than 1 live conductor connected.
3) Is there a fused spur (FCU) visible anywhere near your washing machine socket that switches the socket on and off?