I used to be on verizon. And when I went to the UK I knew I needed data for about 3 days so I just paid verizon the $20 they wanted for a measly 100megs of international data. However, that was a mistake because I only got 1 bar of 3g but it was so inconsistent I couldn't even send a single email successfully. This past january I went to asia and now I'm on GSM so I just bought a $9 sim card at the airport with 1 gig of 3g data. Their 3g is faster than our 4g. But I don't believe that will be the case in the UK. Thats the way to go but I don't think that will work for you since you're on CDMA. Go borrow a GSM phone and add your google account to it.
I no longer charge my phone to any outlets overseas because I just don't trust it. In australia, I had bought a very expensive converter with built in surge protection. It was very compact and adapts to many countries. But at the hotel, it blew up. Even blew up the tv in the room and left a black mark on the wall. Ever since then I only charge my phone through a power bank. I'll risk the powerbank exploding with the outlet but not my phone. So I buy the all in one el cheapo converter (currently using one by conair) which I use with my powerbank.
Look at anker powerbanks. They've been doing that for a while now and I have 2 previous ones that I liked. If its just your phone then 10,000 mah is more than enough. You can buy a larger one but then its heavier and physically larger. Just look for ones with 2 usb ports. There aren't many powerbanks out there with type c and I'm not sure if any can rapid charge your 6p. Which means whatever you buy now you may end up replacing in about a year for a rapid charge version so maybe buy a cheap 6,000mah for now.
