There have been no scientific trials that prove that CoQ10 works with people that take statins BUT... I attended the HEART UK (cholesterol charity) conference last year and this was discussed widely with Doctors and Consultants. They have seen patients energy levels etc improve after taking CoQ10 but it would need to be 200 - 300mg daily.
It is fairly expensive (I pay £24 for 45 days supply @ 200mg) and I was told it wasn't available on the NHS. I shall ask my GP at my next visit though just to be doubly sure.
You can get more info on cholesterol and statins at the HEART UK website: www.heartuk.org.uk or their members forum:
http://heartuk.healthunlocked.com