I think at night all the surrounding hills spill cold air down the Esk valley and we're slap bang in the middle of it. Having the boat out of the water is making a massive difference to how hard it is to keep us warm and condensation free. If we were in the water supposedly we'd see not much less than 10C on the hull below the surface, rather than -11C. But then, here's the tidal river Esk at the moment, at high water so full of seawater as well as pack ice:
The river Esk, Whitby, North Yorkshire an hour ago - taken from about 30 feet above the water

As a result of all this we've actually got loads of exciting things going on:
Ice forming on the walls alongside our bunks - despite it being t-shirt weather now inside with the Eberspacher on.
The toilet wouldn't pump out as the outlet pipe had frozen solid. I'd rigged it up with a pipe from the normal hull exit point, into a bucket on the ground. This has the advantage of not revealing to all in the vicinity that you've just 'been' - an excellent idea from our friend and fellow liveaboard Terry, in Plymouth - but I don't think he expected us to be using it in weather like this! Despite attempts with hot water, at both ends, I've had to give up and we now have the bucket strategically placed beneath the hull, about 1m below the hole. I'm looking forward to the yellow icicle
We couldn't make hot water since yesterday though because it was so cold the gas supply to the cooker stopped - had to buy an electric kettle in an emergency 10pm polar expedition to the Co-Op Pole.
This morning the Eberspacher refused to fire up. I had to unplug and re-plug all connections - including the ones at the unit itself which involved a 6am, -11C, numb fingered spelunking expedition into the depths of the cockpit locker before I could get us cosy again.
We've run out of water in the onboard tanks now also, and the yard tap is frozen solid, so all water has now to be gathered from the yard loo sink, one cup at a time, into a 5 litre carrier. This is for tea/coffee, teeth and washing, cleaning, dog and washing up. The sink is tiny and the tap low, so a cup is the only thing that will fit underneath.
Found a solution to the stove problem - fan heater in the gas locker. Safe? More safe than not giving Rose her cup of tea in the morning
These things are all rather fun and memorable, but unfortunately Rose has got some kind of flu and I've put my back out
Cruising in the Med sounds like a nice idea