Update - It's fixed!
My friend who does car diagnostics did a check and came back with no signal from gear position sensor, after digging down the EPB fault. I then had to remove the air filter box to find it.
So it turns out that the Gear position sensor had not been reconnected properly, so it fell off. Also note the hanging cable support. The garage (not the one who did the clutch) has given me some replacement bolts, which I will refit after sending this post.
Happy ending!