We have the same problem here, theyre always driving round. Usually use some excuse to try to come inside with querry or been sent to see boss in office.
We got turned over 2 years ago, but, it was druggys i think they mainly trashed the place looking for cash. Actually smashed cupboard & filing cabinets open that were not even locked.
We lost pc, moniter & lots of small power tools. Left pressure washers & generator.
We was in the same boat as Ronnie all our customer info gone, but, luckily we had backup only a couple weeks old.
We then increased security, we have steel rear fire door, locks & bolts on roller door, Steel bared outer door for front door & new alarm. So hopefully we are alright now.
But, actually selling most of my stuff at minute on ebay, so nothing left to steal
Gary