Max, you've asked some important questions...but you may not like all the answers.
You say you're moving for personal and professional reasons. Some answers are going to be dependant on what you mean by that.
"I'm sick of working in the US and I met a British woman online who seems to like me and so I thought 'London sounds cool' and I might try to get a job there." -- you'll be returned home at the gate
"The company I work for is sending me to their London office and since I just divorced my wife and have no children, there's nothing holding me in the US anymore." -- your company is probably going to take care of getting your work visa and applying for a National Insurance number.
"I met someone online and we've been dating a while. I can't stand this long distance anymore because I know I want to spend the rest of my life with her. Since I am in IT, I can pretty much bring my work wherever I go. Besides, work here right now is almost non-existant. London may be better." -- You'll need to propose and/or marry and then apply for a National Insurance number the minute you get a proper visa to live here, be it fiance, spouse, whatever. You
do need one in order to work. In order to get one you have some red tape to cut through...at INS (Immigration and Naturalisation).
Freight...can't help you with the question, but others have shipped things across ahead, and brought things with them as well. I'm sure you'll be hearing more.
Cell phone (called mobiles here) ... I've got one, as most people do here (they are very prolifent), but I don't recall the exact procedure, which I am sure may not help you anyway because I've lived here almost 6 years. I have credit, I have a home address, a checking account, etc. You will need to fill in some paperwork and have some sort of credit. Barring that, you may have to opt for a Pay-As-You-Go. Time involved? Seemed almost immediate...as in, how fast can you charge up the battery in the phone?
Driving License...Sadly, you can't just trade like for like. You can drive on your US license for up to one year after you have entered the UK under the appropriate visa. But you have to go through all the tests and start all over. Written test/driving test/minimum eye test. And it takes a while to book, so start early. Suggest you take lessons. (I took lessons and I'd been driving for 30 years...they helped big time.) US license is accepted at UK car rentals. But your US insurance won't be good, so drop it as soon as you leave the US. You'll have to take out the rental insurance until you're established with some here. (But, if you're not going to own a car here, then I don't imagine you'd get insurance.)
Dealing with Brits...many faux pas, but on the whole they are very exposed to American television and films, so just be yourself. You're more likely to amuse than offend, charm rather than annoy. Just don't talk like you know every thing and they don't. If you show respect, you'll get it back. Saying "hi" to everyone you pass on the street may surpise people and throw them off guard, but they'll walk past with a smile for your effort. You'll soon learn the words you're not to say in polite company...and may get a shock over what they say freely. Television is an interesting experience.
