I may be too simple minded, but to me it beggars belief that they can arrest you without any evidence at all, just because you happen to be the landlady of the flat concerned. What grounds did they have for their "suspicion" that you had been handling stolen goods?
Yes, it was reasonable for them to question you, but it is not impossible to do that in a sensitive way without going through the arrest procedure and taking fingerprints and DNA (which, of course, will be kept on record permanently unless the Government actually implements the EU ruling).
You really must get a solicitor before you have to go back, & make sure you are not interviewed again without the solicitor.
As for MWB's post, its a pity that some posters on here seem to delight in putting on moronic idiotic useless posts. You should have enough humanity to understand that this is a serious matter & not one to be treated in such a manner. You might think your post is humorous but it isn't - just pathetic.