Is it possible for me to connect wireless headphones to my tv via the YouView Box please
Not directly. You'd need to take the audio out via HDMI or optic fibre to an external source that supports Bluetooth. My set-up goes HDMI to the TV for video and audio and then optic fibre to a sound bar that has Bluetooth...
One issue with Bluetooth is that it can add appreciable audio delay although a lot better for the latest spec and devices. Not really a problem for something like football commentary but could be noticeably out for lip-sync with a talking head programme. I use RF wireless headphones with my TV set up which do not have any audio delay and also has a greater range than Bluetooth allowing me to wander round the house and down the garden (eg during pre race coverage before an F1 race starts).