Had this on my Mk5 and it was only down to the release mechanism under the bonnet getting gunked up and the latch was stuck.
If the cable has snapped them there will be no tension at all on the release lever in the drivers footwell.
If you get someone to pull the relase lever then you should be able to see it moving back and forth under tension at the bonnet catch (It comes in from the left).
To free up the sticking catch I got a small screwdriver and and rag to clean as much gunk out of the mechanisn (where the bonnet U goes into) then I gave it a spray of WD40. Pull the release lever in the footwell This freed it off initally for me, and you will see the latch will have moved into the middle of the mechanism. Alternate pushing the latch back into the locked position & get an assistant to pull the release in the foorwell to free it up some more. This should free it up nice and good, then give it another spray of WD40 for good measure.