Mortgage renewal advice?

We are due to renew our mortgage soon having had a 5 year fixed rate when we started payments. Neither of us are financially minded, so would appreciate some help. Can we expect to pay more fees even if we stay with the same lender? Are you penalised for staying with the same lender (in the way you are if you stay with the same utility suppliers)? The answers to these questions, as well as any general advice would be appreciated!