Went in for a full test again (I was just over the 30 days so no re-test)
Emissions passed (thanks steelroe) but *dun dun DUNNN* they failed me on "spongy brakes".
He looked a little shocked when I pulled out the previous months test form and advised him that they were perfect just over 5 weeks ago, and I happen to have driven the car twice since then.
I appealed at the front desk and they brought out the head guy. Who gave them a quick go, looked confused and said "Right. Ill sort it".
Lo and behold, a pass.
NCT having dodgy practices? Noooo.