I just went through the same decisions. I moved a 2300 sq ft house. I moved some furniture and gave some away. I didn't really try to sell too much/any of it, because the stuff I was getting rid of had reached the end of it useful life. Also I didn't want the hassle and stress of trying to get rid of it.
Getting rid of most/all of your electronics is generally a good idea. Sell the TV's, the blenders, the microwave ovens, whatever you might have that plugs into an outlet. In most cases you can move your computer(s) though.
The cost differential between moving X and X + 10% is not a big deal, so a lot of stuff "on the fringes" got moved. A lot of the decision depends on your situation. You probably have spent a number of years buy this and that and the other thing to populate your house. That really adds up when you think about it. Even if you sell it all, your are probably going to spend more on replacing in then what you could sell it for. Also a lot of the little things will add up, like pots and pans, other kitchen stuff as well as book cases, etc.
A 20ft container would be about 2/3 of a 2300 sq ft house, from my guess. That is what I what I ended up with though I only ended up moving about 6000 lbs (I think a 20ft normally holds about 8000 lbs of household goods). With insurance you should be paying between $1.00-$1.50 a pound for the move. So I guess that is what you should consider. If you can sell it for more then you can move it, sell it. You don't have to run around your house with a scale, but that might be an easy way to figure it out.
Are you moving into a mortgaged house right away, or are you getting a flat for a while? If you are getting a flat, a lot of them in the UK are furnished. So you could pack up and move right before you go over there.
Also, maybe a corporate apartment in the US before you go, which is the route I chose to take, might be the best way. I got rid of the house about 8 weeks prior to me leaving and everything is moving its way over now, so I will have all my stuff by the time I get there.