I've seen something a long time ago, but can't remember where, where someone took the door off the fridge and used something like Kingspan to build an insulated box that butted up to the open fridge.
This isn't what I was thinking of, but I like the idea Conical Fermenter fridge - Home...
Fermenting for 18 days and then kegging and conditioning for a week is not how you make lager.
You need to use a lager yeast and ferment at an appropriate temperature, may be 12 centigrade for 3 or 4 weeks. You then need to lager it for a few weeks before kegging.
However, as @Leon103 says...
I baked my second sourdough this morning using Shipton Mill's Organic Light Malthouse Flour for the bulk of the flour and a 330ml bottle of home brewed stout instead of water. It's a delicious loaf. If the first two are anything to go by I will have to bake every other day to keep up with demand.