Your first contact with the police can be anywhere, but if this is a result of an ongoing investigation, then it could be that you are asked to come or go to the police station for an interview.
DO NOT say anything until you have seen a solicitor, as with the whole system, a lot of the evidence brought before a court is either directed to or pointed out by, the defendant. The other thing that talking to the police does is enable them to disprove any little thing you may say, thereby casting you as a lier, which makes their case as in duck's arse tight!
Never go willingly into a police station, if asked. Ask if you are under arrest, if not you are only required to give your name and address to an officer, if they would like to talk further you can make an appointment, at your convenience! If arrested, ask for the duty solicitor, or make the phone call to a family member to do the organising for you.
I found the experience very clinical, but previous extreme life experience has made only the very dire prospect of extinction, of any real concern to me. If you have no fear, then you are very dangerous, or stupid!
As you would not be reading this if completely whacko, I can assume the point is not lost that some of our police will get a little "heavy" if they think it will obtain promotion. That is why I would make as much noise as possible, until you get to see your solicitor. The police then know you will cause more paperwork if bullied, than it is worth.
Of more importance is the fact that keeping a degree of respect on both sides is in everyone's interest, they have a job to do, you wish to go home as soon as possible. They can make you stay longer just to be bloody minded, so be reasonable, if given the chance!
However, never take your eye off the ball, the police will only ask questions of people they feel will support locking you up for ever, they will miss out obvious supporters of your side. Surprise, surprise.
Keep to basics and never ever get angry, it leads down a dark ally to all consuming nastiness.