Is anyone aware of a site that would allow me to say "location X, pole height Y, turbine power Z" and get an expected energy yield from a wind turbine? Sort of a wind equivalent to PVGIS at https://re.jrc.ec.europa.eu/pvg_tools/en/

PVGIS indicates I'd need a 40kw array to cover 100% of my winter demand (simplistic - I assume I can always generate, store and recover enough daily) which is quite a whack. I haven't yet run the sums to see what a sensible array size would be to summer generate, sell surplus to grid, use money to offset winter draw from grid, but I suspect it might still be a chunky array.

I'm interested to know, for a given size of turbine, what wind based power production would be for my location (anecdotally it's the first hill since the beach and typically quite windy) so I can do an ROI compare against solar.. I just can't find a decent calc

Turbine manufacturers will publish generation figures for their models at given wind speeds.
There is no susbstitute for on-site wind speed monitoring though, in the exact location and height.

You need to get at the wind speed performance charts for turbines you're considering. Two, different, say, 5kW machines can have significantly different characteristics such that one makes more of low end wind speed and the other, more at higher wind speeds. On top of that, different sites have different wind speed variations and qualities, as well as averages. So, for two sites that have the same average speed, one might get days of nearly no wind, countered by days of lots of wind, while the other, a steadier supply of wind.

As general rules; "cleaner" wind is better. Obstacles and stormy weather cause hard to harness gusts and turbulence. A clear site, free from trees, buildings and whatnot is important. And obviously, higher is better

All that said, yes, you can use the above linked rensmart map with the manufacturers data. When doing this with my own machine, I get about 75% of expected annual production. Or, the wind map overpredicts by 0.5m/s, which ever way you look at it.

Something else to consider; there are runs of days when the turbine makes no meaningful production.