The food department:
Ranch dressing mix. Lived without this just fine until I went on Atkins, and then it became indispensable.
Black turtle beans. I finally sourced them in London after about a year, though.
Liquid Smoke seasoning. I occasionally use this in crock pot recipes. If you use it at all,
bring it over--you'll never find it here.
If you regularly cook Mexican food then bring everything
you will need, as far as it's practicably possible. Almost nonexistant here, even in London.
With my partner's help, I actually hauled over my entire set of high-end pots & pans (Calphalon), as well as my cooking knives, on various of my visiting flights before I got my first long stay visa. I don't know what
would have happened if Immigration had decided to open my bags--I was, in fact, on legitimate visits and had US ties to prove it, but it would have been equally obvious that I was gradually moving to Harrow.
In any case, I'm glad I brought the stuff over because it would have cost double the original price to buy it again here, and I use it every day.
I have been very disappointed in the budget and mid-price bakeware available here. If you want to go high end, it costs an absolute fortune, but you can get pretty much anything. Except bundt pans, bring one of these over if you plan on bundting much.
General advice, if you are planning to bring any bakeware then make sure you check the size of your oven first. Much of the stuff I left behind in the US would not have fit into my oven here anyway.
The pharmacy department:
500 or 1000 count bottles of ibuprofen. I REFUSE to pay exorbitant British prices for a paltry pack of 24 pills.
Melatonin--I use this to catch up on my sleep or to help with jet lag--available over the counter as a supplement in the US, not available at all in the UK and only by prescription in other EU countries AFAIK.
Murine ear drops to keep wax under control, along with the bulb syringe that comes with them. And hydrogen peroxide. Why these items are so hard to obtain in this country, is completely beyond me.
American athletes-foot medicine works MUCH faster and more completely than the British equivalent. (A completely useless fact until you get a flare-up on a camping trip....)
And finally, cough drops with proper dextromothorophan cough suppressant in them.
Something else you can find in any American grocery store checkout line, but is only available on scrip in the UK. My first winter here I got the typical "moving continents immune response," a/k/a "no immunity whatsoever," and spent a little over a month in bed with the flu. Up all night with terrible coughing, and my partner was working abroad so here I was, sick and completely alone. Didn't think of visiting the doctor because I thought I wasn't entitled to NHS care on a student visa. In desperation I called up my partner's mom, who is a retired nurse. She recommended creosote pastilles for the cough. I have to tell you that this was the worst thing I have EVER put in my mouth, bar none. Since then I load up on American cough drops whenever I am back over there, just in case.
Wish I had brought the cat, but I couldn't do that to him. He went to a good, loving and stable home even if it was
with my ex.
Now I travel so much with my partner that it's totally impractical to have a pet at all. Still trying to work this out, and in the meantime I've made friends with most of the cats on my street.