Hi there.We were in the same boat as you. Got our visa's (175 using an agent) and validated them then baby number 2 came. We did the child visa application ourselves and like you said saved a good few pounds. The process is very straightforward. You get a checklist when you download the application form so it tell's you exactly what to send off. We got a reply within a week via email from our case officer informing us to have medical done for the child and police check done for ourselves. She said the application would take 6 months and it did to the day. We sent our application to the London office. Good luck.