Issue has now been sorted and I am backup to full speed, engineer diagnosed a blown isolator in the box on the wall outside the house., said it was probably caused by a power spike during the engineering works that took place a few days ago.
Engineering work in readiness for 1gig to launch next month in my area so looks like I will be upgrading soon and getting a hub 4.
Keep up the great work at Virgin Media, service has always been top notch for me all the way back to the old Nynex days.