Is there any method to show\ record access or access attempts to my mailbox? ⋮
No. The best you can hope for is that a forum team member looks into the matter to see if the server logs show any unusual activity; be aware that it can take them a few days to work through to your post.
I am surprised they have looked at it so quickly. Virgin Media is being hit hard by the Sentry Scanner using password lists etc. They won't formally admit this, but trust me, the scale of hacked passes on Virgin is growing. If you see any unusual activity on your account, then change the password right way to something that would be very hard to guess or Dictionary crack.
Do you mean you have already reset the password? Inspection of the mail logs (for your Forum-registered email address) are not indicating any activity for the 30th. I shall send you a PM (purple envelope top right) in a moment so we can identify the email address and affected date.