The existing system works perfectly, with very little increase in costs (the major engineering works were done years ago, Tea after TV has long been part of British life!), so there is no need for a compromise like load shedding.
Electricity networks are all about ensuring there are multiple independent ways to deal with uncommon problems, so that you don't get failures.
If you get an uncommonly dry season and the reservoirs are empty, then the BBC will be forced to stagger your coro, or more likely you will get in line at the post office and receive ration-books for your tea breaks ;-P
It hasn't happened in the past 30-40 years that this system has been running, about the only thing you can count on in those parts of the UK where the hydro is based is rain...! I think the investment needed for such a remote possibility isn't warranted, especially as water supplies dry up fairly slowly so there is at least some warning to start rationing the tea-bags. Coronation street is ITV by the way, the BBC will be staggering EastEnders. The best way forward is probably to axe such shows....(dreams of more room for better programmes on TV..)
Edit: just noticed polishaw saying UK had a 100 year drought in 2011. Also STOR and Triad mentioned above are load shedding. Following is musings, not facts :)
New Zealand has mostly reliable rain, but a few years back it had a national drought which caused noticable economic problems (Noted that the problem was due to lack of power and the forced changes to control power usage - not so much due to load management!).
If the UK had a drought, I suspect there would be a lack of hydro power, and that could easily have some interesting effects upon the network. Yes there is plenty of fore-warning, but that doesn't mean it wouldn't cause difficulties.
Also in New Zealand the constraints on hydro-electric have been slowly getting more restrictive over time due to eco-friendly rules (min and max outflow rates, min lake levels). And if the UK is anything like New Zealand, over decades the network load will increase but hydro-electric capacity will remain fairly static.
We did indeed have a drought in 2011, and there were no ill-effects on this system. That's the point. Water shortages in the UK tend to affect the southern end, and most of these hydro buffers are up north, where they wish it would stop raining.
Increasing loads on the system won't really effect this type of setup, hydro is used as a peak buffer not for base load, peaks like these will tend to have the same order of magnitude (they have over the past 40 years while base load has increased).
There are other issues with power in the UK, but dealing with post TV tea peaks isn't one of them, and isn't worth investment which could be spent better elsewhere on the grid.
The drought only really effected the south, the north and Scotland still had less water reserves than normal but plenty of capacity left. The hydro generation is mostly based in Scotland.
There is also a Welsh hydro-electric dam, excess capacity from the grid pumps the water up the mountain during the night and then it's released as and when.
