Yes, and some people on Octopus Agile have been seeing negative electricity prices as consumers recently, although that was due to high winds hitting the offshore farms rather than solar.

The App for my Bosch washing machine does have links to a couple of proprietary ‘smart home’ solutions that can synchronise start times with solar output, but none of them are compatible with my other kit so I never looked further. It does also support IFTTT so I guess I could set something up myself if I had the skill.
Start times are better than nothing, but what would really be useful is the ability to modulate the heater output to say 1 or 0.5kW over a longer period if there’s thin clouds reducing the output from the inverter. Also cross talk between appliances that allows you to turn them all on at once, and they can introduce pauses in their programmes, so they don’t overlap high power tasks.