Check the bands available though I would imagine it’s the same as Vodafone.
The FP4 connects to the following 5G bands
Sub 6 NSA bands:
n1/n3/n5/n7/n8/n20/n28/n38/n41/n71/n77/n78
First check what Virgin are offering:
Check the list not everywhere is covered by Virgin
See if you can borrow a Vodafone SIM to ensure your SIM is OK
See also the following which indicates no 5G for Virgin though I doubt that. Didn’t check the age of the page