Police officer in UK is hounding me

Hi I got pulled over by the police in my van the other day as it was showing no insurance and I explained that I have insurance but had only insured it the previous day and am waiting to receive documents which I Will forward to him. He then went onto say that he had seen me driving my partners car and he had checked the insurance and I wasn't the policy holder which is true, I thought I had taken out fully comp but turns out I am third partie for my van. I was never pulled over in my partners car he just said he will contact me this week to make sure I had insurance on the van but will talk to me about my partners Car for no insurance. My question is can they proceed with this investigation without giving me a producer or caution etc and what do I say to him when I speak with him.
Kind regards
Colin