All of the UK is small enough to be in the same time zone, so just pick anywhere in England and it'll be the same. London is the obvious one to go for. Brighton is directly south of it - less than an hour on the train! There are people who live there and take the train to London every day for work.
If you're on Eastern time, it's 5 hours ahead; if you're on Pacific time, it's 8 hours ahead, and I'm sure you can work out the rest from that if you're not in either of those zones. The UK doesn't change to and from Daylight Time on the same week as the USA so at those times of year it can be an hour out from that for a couple of weeks.
Just out of interest, if you ever want to visit the UK, it's a real pain. Most flights west to east across the Atlantic go overnight so you end up at the English airport about breakfast time with your body clock thinking it's still the middle of the night - and you feeling totally zonked if you haven't managed to get any sleep! When I come home to London from the US it's a weird feeling - fortunately as British coming home, immigration never ask any questions when I show my passport - and all I want is to get home as fast as possible and get into bed. Sleep is instant, then I wake up about lunchtime. So if you ever do it, don't plan anything for the day you arrive. It'll be fine next day, and going in the other direction is nowhere near as bad.
The British Isles is mostly comprised of a long and thin country running North-South, so most of it fits within a single time zone. This is known as Greenwich Mean Time (GMT), it is within a few microseconds of the scientific time known as UTC. In the summer we advance our clocks by one hour to British Summer Time (BST).
Most of the world, especially the USA, seems to think that we only have one city - London. So if your clock shows "London time" or GMT (remember to adjust for summer) then that will be same for everywhere in the UK - even Brighton.
To put this into perspective for you, take a look at the map below, showing the whole of the United Kingdom, England, Wales, Scotland and Northern Ireland over a map of the USA.
The UK is all in the same time Zone so if your clock shows London then it is the same time across the whole of the UK
Same as London.
Use London. UK is all in the same time zone.
Same time as London you dolt
Either look up BST or GMT.
