Thanks for the suggestions. I’ll probably end up with your reccomended route as you’re the professionals (and I’m still learning 
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id highly reccomend avoiding the A605 its a Nightmare…i would follow the a14 all the way down and jump onto the A1 north. personally. You would probably save 15 minutes. Not much but pffft.
A47 Kings Lynn via Wisbech - A47 KL - Swaffam -
But take the A1101 to Swaffham via Downham Market if going this route, it cuts a few miles off the journey…
I normally take the A11, A14 route, its quick easy & kinder on fuel consumption, normally.