Hi TravelMom,
I don't know what a "Charging Block" is, but in the U.S., you likely use chargers which plug into the wall, and have either one or two USB ports. Typically one port is labeled 2.1 amps, and the other is labeled 1.5 amps. If you look at the tiny, tiny print, they will all say "100-250 volts". So all you need is a simple adapter to connect the two US prongs to the two big rectangular jacks on the UK socket. The adapter may or may not have a third ground pin (round), but it isn't needed. If a charging block has multiple sockets to plug in two US chargers, that's fine. I usually travel with 3 or 4 of the chargers with double USBs, as many hotels will not have enough open outlets. On rare occasions, I've had to unplug a lamp to have an open outlet to use. Of course you will also carry the USB cables for your phone, I'd recommend being sure the ones you have are all 6 foot long, rather than the shorter one. Reason is that many times the outlet isn't that close to my side of the bed.
I was in Ireland a month ago, and saw that ALL the outlets, had an on-off switch, so be sure the switch is "on". If an outlet is still dead, there may be a card switch on the wall by the door, where you have to put your room keycard into a slot to power up most of the room.
You may even find a few hotels have USB jacks on lamp bases, that's safe to use. We were in a hotel in Ennis that had a two foot row of outlets of every nationality, including a U.S. outlet. I should have counted the outlets in that room!
When we go to Switzerland, I just carry a few Swiss chargers that have the two small round pins. They take up less space than those gigantic British plug adapters.
Caution: The above is true for cellphone chargers, but other devices, especially heat producing curlers, etc... may very likely be 115 vac only, and will make smoke if connected to the 240 vac in Europe.
