Xerox never came out with a GUI product
The first Xerox GUI product was the Xerox Star in 1981.
I took my laptop from Oregon to London last summer so I could send email to my family and log my geocaches.
No problem with wi-fi. It worked for me exactly as it does in the states. Channel selection is made by the access point, not by the laptop, so it's not your worry.
Your laptop charger has a label telling what input voltages it will accept. All of my chargers (and my electric razor) take 100-240 VAC and 50 or 60 Hz. That means they don't need a transformer to work with England's 240/50 power, just a cheap mechanical adapter which I picked up for a few bucks.
The Boingboing discussion of "Geek Atlas: 128 nerdy must-sees and an education in science, technology and geek history" describes a good reference.
I can recommend the The American Museum of Radio and Electricity in Bellingham, Washington. My daughter and I dropped by for an hour and found ourselves staying until closing time.