Just to finish off this thread if someone else comes across it from a search.
The broken wire was *one* of the causes of the flickering, but there was also a problem with the LCD screen not making proper contact in the instrument cluster..
So here's how I suggest you can do it (NB this is only my comments, I make no guarantees or promises, so PROCEED AT YOUR OWN RISK!)
Firstly remove the cluster from the bike. You'll need to take off the windscreen, mirrors and fairing (inners and main fairing).
Note that there's a stupidly tiny bit of plastic at the front of the fairing between the top and bottom section which will break (as I found) if you aren't very careful
)
You may also need to remove the section that holds the headlights to get at the screws behind the instrument cluster.
Also unclip the connectors at the left front of the bike that go to the wiring on the instruments and headlamps and the ones behind the instrument cluster.
These clips can be a bugger to get loose if they've not been taken apart for years. The rectangular one has a clip on the top which needs to be pressed down so you can wiggle them apart, but the more rounded one with the "tubes" for the wires has a clip that has to be lifted *up* to disengage it.
Then gently wiggle the parts and, eventually, they'll separate, but try very hard *not* to pull on the wires as you risk them coming off the internal pins (which is probably what caused the loose wire problem I mentioned in an earlier post!)
Once you have the instrument cluster free, using a junior hacksaw, cut a slot 3mm from the back edge. This will enable you to remove the back whilst reducing the risk of damaging the circuit board inside.
You can use a Dremel or other rotary cutter which might be quicker, but the thickness of the cutting blade may make it more difficult to reassemble the cluster as you'll lose much more material between the sections and has a greater risk of error.
Start cutting on the side of the select/ reset buttons as there is more space between the plastic and the circuit board and this will give you more leeway to get used to the feeling and make mistakes!
The casing is approximately 3mm deep, so cut carefully until you can see through to the inside (use a thin slip of paper to carefully check that you've made it through), then slowly extend the cut around the circumference of the cluster.
I found it helpful to put a flat-blade screwdriver a couple of millimeters into the slot and very gently twist it so I could see how far the cut had actually got and expand it very slightly to make cutting a bit easier.
Take care when you get to the two "corners" on the side with the instrument lights as the circuit board is close to the case here. You need to check you're no more than 3mm from the back edge of the cluster prevent the risk of damaging it.
Once you have completed the cut, it will be possible to separate the two halves and then slowly manoeuvre them so you can straighten the wires from the connectors.
The pictures in the link from the earlier post show the wires coming out of the back of the cluster, but not the back section which appears to have been removed entirely. It is possible to gently turn the back section to get to the securing screws (which are numbered) and remove them to get the LCD section out.
Once you've done that, plug it back into the bike and try pressing at the corners to see if the flickering starts or stopped. I found that if I put a thin piece of plastic from a milk carton under one corner, it stopped the display vibrating and (mostly) fixed the problem.
If you want to go further and remove the blob of sealant and take the whole things apart, you can, but I didn't go that far.
I sealed the unit back up with electrical tape aroung the sections where I cut it until I can think of a better way to keep it together which doesn't involve gluing it again!
Hope this helps