As no one has come back to you here goes .....Unless I am way off mark, and unless the DVD player is also a recorder, I can't see why it would need to be connected to your aerial by an RF cable.
I have never had a BT box so I am assuming that you have the wiring details supplied by BT but here's a link to the PDF if you need it.
http://www.productsandservices.bt.co...tall_guide.pdf
An RV cable connection to your Smart TV is always handy in case your BT box dies as you can tune the TV in to Freeveiw etc .
You will need both of the HDMI cables to transfer the decoded signal from your BT box to your TV and when you use your DVD player.