Ollie, I had same problem in a Escort Van. Believe it or not it turned out to be the rear light bulb holders. Van would still run till you hit the brake!
As per fuse box I got mine off your bro for £200 iirc. He got the one specified for my Cos (£100 odd), but it had wrong part number on it. So he got me the one matching mine and it was £50-£100 more
Corrected all my problems, but my standard boost gauge, etc dont work anymore
Think we missed a connector somewhere!