If you've used the "clear & delete everything" option, then this is a slight case of sledgehammer & nut when you could have deleted recordings using the "my shows" view, but what's done is done. And yes, there is a known issue with this option - see the pinned post at the top of each TV section of this forum .... https://community.virginmedia.com/t5/Virgin-TV-V6/Known-Issue-Clear-and-Reset-Function-V6/td-p/5161386
Having said that, you should be able to recover your V6 by using the following sequence..
Try turning off the V6 at switch; then on the V6 box hold down both the power button and the +button at the same time. Then turn on the V6 again whilst keeping hold of those buttons for a further 30 seconds. The box should reboot, the power button should turn blue, and it should reset and boot up normally.