The financial hardship is a big problem I think everywhere. I'm particularly delighted to hear that England and Wales pay up to £100 a day. That is many times more than most state courts pay here. Typically the average juror payment is about $22 a day across the states, with some states as low as $10 a day, which is barely enough to get a meal at a McDonald's or parking for your car.
There are a lot of jurors who cannot afford to serve if they're empanelled on a trial for longer than a day or two. They would be excluded from longer trials. Typically they are able to come in for at least one day. Most jury managers will work with jurors so that if they have a day off or can pick up an extra shift, we'll make accommodation so that they are able to serve at least for that day.
In the United States, most trials are not that long. A typical trial is probably one to three days and many cases are only one day. It's a day's worth of wages that is lost, but often many of the people who are on hourly wages can make that up by picking up an extra shift at work, or something along those lines.