Tedob1 is right - the knowledge I have of police raids on paedophiles and the like - they always turn up scores of images, documents and other evidence of their nefarious activities.

These people tend to covert their collections and rarely part with them, and it is generally not a passing whim, it is an obession - so there is generally tons of evidence pointing to their activities. Hence your visit from the constabulary.

Good advice has already been given here but I will stress it again, get expert legal advice before speaking to the investigating officers again - I really think they are drawing a long bow in trying to make the connection - but given the evidence in their possession it was something that they had to check.