Electronic power converter

You have to look at the small print on the labels of the devices themselves (or their power supplies).
If it says "120-240V 50-60 Hz ~", or something similar, it will be OK.
If it says "120V 60 Hz" then it is designed for North America only, and it is likely to emit smoke, or a burning smell and never work again if you plug it into a 220V 50 Hz AC socket.

Most modern PC and telephone power supplies should be OK, but check the label yourself.

Check all your electronics chargers and you should see something like this:
"Input: 100-240V~50/60 Hz"
Is so, you're fine.
The hair dryer, on the other hand, is a whole different animal. You will need a converter because it is an electric heating device (as well as an electric motor for the blower). It will self destruct if you don't have a converter. Because of the power levels, it really needs a transformer that is heavy. Better is to purchase a new dual voltage hair dryer or rely on the ones usually provided in better hotels.

Hi Jerry:

Having recently taken a month long vacation in Scotland, England, and Turkey I have some experience with your issue. You should look at each appliance to see if they work on both 120 and 240 volts, and work on 50 cycle power in addition to 60 cycle. All of the items that you list with the exception of the hair dryer should meet these criteria. For these appliances all you need is an adapter that lets you use the existing cord with the UK and with the France outlets (they are different). The hair dryer probably does not meet the criteria in which case you will need to purchase an expensive transformer to adjust 240 volt 50 cycle power to 120 volt 60 cycle power. Or you can purchase a hair dryer in France or the UK that will work; you will need to purchase a plug adapter to let you use it in both nations (actually UK and continental Europe). I would say that you should look carefully at any appliance that either consumes a lot of energy and/or has a motor. The last thing you want to do is to plug a 120 volt appliance into a 240 volt outlet.

What I found useful was a power strip that it rated for 240 volts and which has outlets for a variety of plugs. I bought this from an Amazon vendor for about $20. This lets me recharge a number of devices, or batteries for the devices, all at the same time.

Check out the Rick Steves Travel Tip:

http://www.ricksteves.com/travel-tips/phones-tech/electric-adapters-converters

I have two small hair dryers, both of which have a switch to convert from 110 to 220. I switched over before I packed - just in case of brain freeze on arrival - and have had no trouble. What I do find interesting is that is the US I have an option for low or high power, but here in France on 220 I only get the low power.

Forget bringing a converter:
http://www.enjoy-europe.com/hte/chap11/converter.htm

Things to check on plug adaptors for the UK/Ireland:

• Live / neutral pins are sheathed
• Earth pin is not sheathed.
• If earthed plugs are accepted, the earth pin must be connected and not made of plastic
• Live / neutral sockets must be shuttered
• A fuse must be included of the proper rating

All of these are required to meet British Standards. Many adapters sold outside of the UK fail one or more of the above safety points.

Depending on your devices, another handy item is a USB charger with multiple ports like this... http://www.ebay.com/itm/Multi-Port-USB-AC-adaptor-Wall-Charger-for-Apple-iPhone-/320708167085 For your ipod, phone, most cameras, GPS, etc that are able to charge off a USB, this acts like a power strip without the bulk and weight. Just make sure the output is compatible with your devices. Outlets are sometimes at a premium in most hotels/B&B.

Many, if not most, hotels will have a hair dryer either in the en suite bathroom or at the front desk (just ask to borrow) -- one less thing to carry. But these may be lower air volume than you are used to. Works for me -- I have never carried a hair dryer to Europe -- but I have also never made it to anybody's best-dressed list.

Very few converters for the consumer market will change the frequency - the 50 Hz provided in Europe to the 60 Hz required by North American machines. Voltage is easy, frequency not.

Frequency matters with analog clocks, and sometimes digital clocks, and with motors. If the motor won't be used for long you may be OK.

But for something like a hair dryer which uses both a lot of amperage and a different frequency, you need a large transformer and regardless of that the life of the motor will be reduced if it is rated 120 V 60 Hz.

As harleydonski and Nigel note, "converters" are not the same as "transformers". I've seen the aftermath of an iron hooked up to a "converter". Leave thermal devices that are not rated for 220-240v back in 120v land.