Hopefully not.Thanks Whitespirit66, the grey wire from the motorised valve links to the "earth" wire to the tank stat. There is no other wire taken from that connection.
Am I doomed?
The earth wire from the tank stat to the valve grey is being used as a control wire, not an earth. It's the cheap and lazy way of having three connections without buying the correct cable.
All you now need is a wire from the programmer terminal 1 to the grey wire (This is in addition to the wire from the tank stat.)
You said that terminal 1 is already connected to the L terminal. It shouldn't be there It is an obvious get-around due a shortage of cores in the cable from the programmer to the junction box. It will be the cause of your problem.
The only way you will solve it is to run a new cable with the correct number of cores.