This was one of our biggest stresses in applying, especially as I had an apartment lease with almost no flexibility. Here's how we solved things:
1. Right before I left for England, I took my car to a big-name seller and took whatever they had to offer. Made sure I had the title and both sets of keys so I could sell it then and there. Then used a rental the next day.
2. Paid the deposit for sea shipment but didn't do the actual scheduling until after I got the visa. However, I had all of my paperwork done ahead of time so it was just the phone call to schedule the pickup and getting people to help pack the crate.
3. While my apartment manager couldn't do a lot, I did give her a heads up about the situation and planned out all kinds of alternate solutions. In the end, I had to forfeit two months' rent to buy out the end of my lease.
4. We bought plane tickets through Thomas Cook as they were very cheap last minute.
5. I contacted friends, etc. to see what they wanted of my stuff and asked them to wait until I heard about the visa.
It is utterly absurd that UKVI puts us through this! But in the end, the visa approval was worth it. We got our email notice on a Friday, and my wife arrived 28 hours later. We got our visa package the next Monday morning, and we were on a plane back to England that Thursday. So in three days, we emptied and cleaned my apartment, sold my car, and took care of all my last-minute details. It was insane and we nearly killed each other from stress and lack of sleep, but it was worth it.