Suddenly receiving relatively large quantities of spam in your inbox is a problem which others have been reporting since about the middle of November 2016, and a problem which Virgin Media accounts had in a big way in October 2015,
What are some of the subject lines of the spam emails? And the content? Do the messages contain links? Or content sent as images? I would expect Virgin Media to take action if you provide additional details. If not, then it is time to switch to a free email account elsewhere which does not have this sort of problem. Gmail accounts have superb spam filtering and many additional features not present in Virgin Media accounts.
Thanks for your response. Mostly are to do with betting, borrowing money, credit cards, health cover and compensation companies. I'very tried to call VM and got cut off after being on hold for 15 mins. Their Twitter told me to try the forum.