I can see why you'd be nervous, but it should hopefully all go OK -
They may ask you questions about work, etc to make sure the terms of the visa are still OK. As long as you have nothing to hide, than all should be straightforward (hopefully). I'm on a work visa and I've been questioned a few times about details of my job, etc. I had one who was really drilling me, but 95% of the times its been pleasant or at least easy enough to come back through.
Good luck!