Uni room inspections

Do you get a warning when your room is going to be inspected and does it actually matter if you have anything your not meant to like a mini fridge in some places

I believe you do get a warning, although how far in advance you get notified will be outlined in the agreement you signed to rent out your room (I had like 24 or 48 hours' notice, I believe). As to if it actually matters if you have something forbidden, well... it depends. In my halls we got threatened with a fine for keeping a rice cooker in our kitchen, so the flatmate who owned it relocated it to her bedroom. On a later inspection of our rooms, that wasn't flagged despite still being against the rules... so it really depends how zealously they police the rules.
I'm curious as to why you brought a mini fridge to your halls. But that doesn't matter too much. It's unlikely you'd be kicked out of halls right away for keeping a mini fridge, but you might be asked to get rid of it (and they'll follow it up with another inspection to make sure you indeed have gotten rid of your mini fridge), and/or get a fine - depending on the halls' policy. The disciplinary policy of your halls will be outlined in your agreement and/or information booklet, which I would read very carefully if I were you.