London You don't need to express interest, and everyone on the electoral role (I think that is the criteria) can be called, and unless you are excused (eg criminal record, mental health etc) you must do it, unless you can get it deferred, for one of the reasons already mentioned.
Given the choice, I wouldn't have done it. As well as being a huge waste of time, I found all the defence and prosecution arguments enormously confusing (I understand that this may be the whole point) to the extent that in one trial, I didn't have a fucking clue whether or not he had done it so had to vote 'not guilty' - you only say guilty if the evidence says 'beyond reasonable doubt'. In that case, the jury discussed it for so long that the judge went on a majority rather than an absolute verdict (I think it was something like 10/2 in favour of guilty).
However, I do have concerns about the robustness of some verdicts. In the above case, I strongly suspect that some jurors voted guilty because 'he looked like the type' and they were bored with going round in circles with the arguments and just wanted to go home (seriously).
In the jury room, its a bit like who shouts the loudest and takes control of the room, and that's not always the person that is correct.
The case was an assault that evolved from some drunken silliness (throwing objects that hit someone - there was no evidence of 'intent') and the kind of thing that TBH, many of us have probably been involved in at one time or other. The defendant was one of a group of about 8 people, identified by a pensioner with poor eyesight looking out of his bedroom window on a dark and rainy night.
I also wonder if the average person is 'qualified' to be a juror. I am a degree educated professional of above average intelligence and I found the whole process really mentally taxing, despite concentrating hard throughout. Considering that the country's biggest selling newspaper is The Sun, and the rise of political parties such as UKIP/BNP etc, is the 'majority' able to make an informed decision on whether someone should go to prison?
In the other trial we didn't even get a verdict, because, despite it being a fairly simple case, we could not agree and could not give a verdict (the defendant was charged with dangerous driving, which IMHO he was absolutely guilty of but he was trying to get off on a technicality and half of the jury believed his bullshit excuse). I don't know what happened to that case afterwards.
My mum has done it, as have several of my colleagues (I would estimate 4 or 5 including me, out of a 40 person office) that I know of.
One of my colleagues got picked for a high profile murder trial, and was in two minds whether or not to do it, because it would have been interesting, but in the end, she decided not to do it because it would have meant three months of work, which is a disaster for us. Again, she was able to cite the negative impact of approx 2/3 months away from work.
Perhaps the location does have an impact on the chance of being called up. I wonder what the furthest you might have to travel would be? Is everyone in catchment?
Where would you serve if you lived on a remote Scottish island, or in the Scilly Islands for example? I assume that you would have to stay near to the court rather than travel each day?