get a freeview set top box with RF loop through. connect your aerial to this, then the box to your vcr scart socket and record off the AV or ext input. If the video has only one scart socket you should connect the vcr to the telly using an RF flylead and tune it in (around ch 36 UHF), keeping the scart for the set top box.
then connect the RF out of the box to your other digital device's aerial input using an RF flylead. then you will be able to watch and record 2 different things.