Mine was lovely and warm when I got in this morning thanks to the FBH doing it's job while I get ready for work :)
It even stopped telling me the washer fluid was low when it was full. Still got the SRS light though 😥
These were mine when I checked them for a another thread. This is for my 2005 L322 and will be slightly different from yours due to calibrated heights and sensor resistance variations. The pictures show the 3 height settings.
I'm guessing @gold rover means this from the one I posted. @gold rover The inverter is an additional bit of kit that gives you 240v off the battery, it's not required for charging.
It links to this but for the extra few quid I'd go for a much bigger one. As said 30w in a scottish winter probably won't cut it. 100w should charge the battery as well, allbeit slowly.
I'm just a lazy git and don't mine paying a few extra quid for convenience. Perhaps that will change when I retire and have plenty of time on my hands.