Hi Adam
Hope the red flags weren't flying when you were out on the ranges! Donyland woods has been off limits for sometime but it was clear the last time I rode through.
Was cold Sunday morning..... even colder up in Thetford but the frozen trails have been far quicker to ride than the gloop!
Try this trail for a colchester based loop.... it's just under 20miles with not much climbing. You can even stop for a pint at the Rose and Crown in Wivenhoe followed by an easy ride home.