But our current grid is quite good at following the gap between essentially uncontrolled-output sources (nuclear and renewables) and demand. Pumped is, AIUI, only really used to fill in when forecasts of other generation or of demand are a bit out and some more electricity is needed quickly to fill in while the gas power stations spool up.

At the moment if all goes to plan it's preferable to generate directly from coal or gas rather than going via pumped storage as there's always a loss and coal and gas are always setting the marginal financial and environmental costs of generation here (we're never, yet, running on just nuclear, non-pumped hydro, wind and solar) so the only “free” electricity stored as pumped is that from when the planning doesn't go quite right and the fossil stations are left running a bit faster than needed. The rest of the time pumped needs to be filled with “full cost” fossil electricity - which is worthwhile as an insurance, of course.

Therefore, its current generation is not necessarily representative of what even the current pumped-storage infrastructure could produce.

Connor, have you looked at http://northconnect.no ?

This is a HVDC interconnector project from Scotland to Norway. Plan is to use Norwegian hydro to backup Scottish renewables and v.v. The Scottish end just got planning permission.

Ah, could be.
Should it be MW. No unit when you download the Gridwatch data and my eyesight is really giving me trouble this week.

Currently showing 0.04GW (0.14%).

Using sea-water in a pump storage system may not go down very sell with the "greens", none of the current wildlife in the top lake area will like it!