Something like this should sort it:
http://www.amazon.co.uk/Stepdown-240-120v-Transformer-100VA/dp/B000NIYF0K
Rent: OK, that's a good chunk of cash right there. If I might make a different suggestion, you'll get far more for your money if you look outside of Central London. For the cost of a 2-bedroom flat in London, you could easily get a 3 or 4-bedroom house with a commute that's only a bit longer. For instance, Croydon or Bromley are both only 15 minutes outside London by train. London is maybe a little cheaper than NYC, although not the areas that have rent controls.
Taxes: Try the salary calculator here - https://www.thesalarycalculator.co.uk/salary.php . That'll give you an idea of what your take home pay will be every month. In the UK, people usually get paid monthly, not bi-weekly. As a US citizen, you'll still have to file your US taxes every year (this can be done through the US embassy or online) and, on that kind of salary, Uncle Sam will probably be wanting a bit of it. Speak to an accountant with experience of filing US taxes as they'll be able to help you with this.
Power: Check your electronic power supplies to see if they will run at both 110v and 240v - most small electronics will work on either voltage (laptop PSUs, phone chargers, etc). For these, all you need is a plug adapter. For anything that won't, buy a stepdown transformer - something like this: https://www.amazon.co.uk/Stepdown-240-120v-Transformer-100VA/dp/B000NIYF0K . Bear in mind, this works well for standard electronics, but for kitchen appliances and anything that includes a motor, this won't work (the transformer just handles the voltage, not the AC frequency). Leave that stuff at home and buy new in the UK. Tip: Bring a few US power strips to plug into the transformer, that way you can have multiple outlets from a single transformer.
Pensions: The UK has a state pension that you pay into out of what you pay in tax (part of your taxes goes towards 'national insurance', which includes the state pension). This is a bit miserly though, so look into paying into a private pension plan too - there are many that are set up like a 401k. Nest Pensions are pretty good.
Transportation: If you end up in Central London, don't bother getting a car. The Tube, black cabs and Uber will get you where you need to go. Get a Zipcar card too, just in case. If you are outside Central London, getting a car isn't a bad idea as things get a little more spread out. You can drive on your US licence for up to a year, but insurance won't be cheap as you'll have no UK driving record.
GBBO: Worth watching for water-cooler conversation. And it goes by its proper name in the UK - The Great British Bake Off. They couldn't use the phrase 'bake off' in the US as it's copyrighted by Pillsbury, apparently.
Thanks - So would this work?
Sorry! Looking for a new one
Get this wall transformer
Something like this? http://www.amazon.co.uk/Stepdown-240-120v-Transformer-100VA/dp/B000NIYF0K/ref=pd_cp_23_3?ie=UTF8&refRID=0E3P6XMAPQDW40WYJ3YW For example.