For some reason the remote locking on my 1995 Punto elx has stopped working, so stupidly I pressed the reset button in the roof console.

I have 3 keys for the car, the red key, blue key and blue remote key.

Does anyone know how to re-code the remote locking on a mk1?

nope but had several of the keys with the button on the edge where the button has come loose from the circuit board - so some patience and a steady hand plus a soldering iron has fixed that - worth checking thats not why it stopped working before going further. You will never get it to work if the button has detached lol.

The key still works, as when I press the button the wee red light flickers on the key.

Also put a new battery in it, but supposedly because I've pressed the reset button in the car, I've de-coded it

Sorry I don't have an answer to your problem, but I would be grateful to see if anyone has an answer. Like yours, the remote button on mine still works, the red light flickers and I have fitted a new battery. Unlike yours, I have not reset it, but is still doesn't work. Mine is a Cabrio and being an early model, it pre-dates the red key.