MARK Group Knocking

I found a story about a member of Mark Group staff calling about loft insulation grants, I had exactly the same experience.  He was putting me under pressure to invite him in to my home to check my loft.  I asked him to leave some information, but he wouldn't and I felt uncomfortable.  Having checked the internet it does seem that it's agenuine grant, but why don't they conduct their busines in a more professional way if that's the case????????????