Thanks to both of you for your answers but I have managed to solve it, finally.
The switch settings that were with the key when I bought it were not the right ones for that key!
After seeing a post where someone had put a picture of a key that was the same as mine and had commented that 4 & 7 on gives £5jp and 10/20 or 30P play I gave it a try and it was as simple as that.
I suppose its simple now I know but I just trusted the settings that were given to me.
Cheers