Posted: 13/11/2013 at 09:20
Good morning Maggie - you livei where I lived for most of my life
I wouldn't worry too much about the part of the trees above ground - I'd be protecting the pots by raising them up on feet so that they drain freely and wrapping them in 2 or 3 layers of bubble wrap which will help avoid the soil from freezing solid and preventing the roots from 'breathing'.
The big danger for plants like these is not cold per se, but cold & wet, so keep them in a sheltered spot against the house and keep them fairly dry. I would only use your fleece bags during very cold spells, and remove them when the weather improves to keep good airflow around them and avoid any chance of damp conditions which might cause mildew and rot.
Good luck, and give my love to Mid Suffolk