Ok. I went out today and it all worked fine. So was it because it had not been started for a month because Mike has been a bit poorly or what ?
So. I took the top & bottom covers off of the steering column and there the little bast**d solinoid was. Basically it's a solinoid that locks into a piece of metal that slides up and down as you move the gear leaver. It is actuated when the engine is started. That is with the ignition switch at the accessory type position, all the little icons alight, the gear leaver travels around quite happily. Start the engine and in goes the little pin and it must be little, because I doubt the hole it goes into is more than 1/8" dia. This solinoid is released by putting your foot on the foot brake which then pulls the pin out of the hole.
So. What was wrong yesterday.
1. Lack of use and it won't do it again. Yeh right.
2. Lack of 12v or a ground, whichever it is, from the brake light switch. Thats possible, but number 2 son said the brake lights were on, so something was happening at the switch.
3. Poor connections at brake switch or solinoid. I took off and cleaned all those.
4. Hole in piece of metal out of line with pin, so it sticks. In case, I just drilled it a bit bigger. Well somewhat bigger. Well about a 1/4" ish.
The leaver still locks as it should and indeed despite the bigger hole there is still very little gear lever wobble.
Have I fixed it, we will see. I will report back if it plays up again.