Vibrating Instrument binnacle cure

To remove the central vent; a broad paint scraper tucked inter the bottom edge of the moulding & using the surrounding dash as a fulcrum, ease the unit out. Originally the seal was foam rubber but in all probability that will have disintegrated, so little or no resistance should be expected.
I have a flexible grabber (expect a comment from Cobber), into which I insert a small magnet, this forms around the curves with no problem. It’s a couple of foot long (wait for it) with a claw on the end, available off eBay & an invaluable addition to a tool kit. Especially if like me you use & drop a lot of stainless nuts & screws in places which are difficult to access
M

Thank you for the responses, most helpful.
I have also googled/youtubed that topic. The example used something like a bicycle tyre lever. I had a tool like that which came with dash cam supply cable fitting kit.
That together with some ice lollipop sticks did the job.

Totally agree about the disintegration of the foam. The remains of that will have to be cleaned out, and something put in its place.

So far one screw removed and recovered.
Just have to work out a way of putting the binnacle back such that it doesn’t move/rattle. 

Airportable wrote: To remove the central vent; a broad paint scraper tucked inter the bottom edge of the moulding & using the surrounding dash as a fulcrum, ease the unit out. Originally the seal was foam rubber but in all probability that will have disintegrated, so little or no resistance should be expected.
I have a flexible grabber (expect a comment from Cobber), into which I insert a small magnet, this forms around the curves with no problem. It’s a couple of foot long (wait for it) with a claw on the end, available off eBay & an invaluable addition to a tool kit. Especially if like me you use & drop a lot of stainless nuts & screws in places which are difficult to access 
M

A couple of foot long…..now you’re bragging!
Reminds me of the old gag……”It’s a foot long, but I don’t use it as a rule!”

Which ever way you decide to fix & subdue the instrument cover, do make sure it is easily removed. How you’re expected to remove the connectors from the display to facilitate its extraction is beyond me, I suspect that the amount of damage to the covers on so many of our vehicles is a direct result of mechanics hands rooting around in too smaller space. Trying to resolve a poor connection or a failed lamp could easily reduce the cover to a shattered version of its former self.
M

Well, ever so near but...!
I managed to remove two out of the three failed clips that were still in the dashboard. The third was a child of dubious parentage. I had to grind the tip of the screw off and weaken the clip. Recovering them through the vent was doddle. Re fitting the vent was easy too after renewing some foam around the ductwork.
With the three clips out I bonded in three rivnuts using 2 pack JB weld repair plastic glue. So far so good.
I then cut and shaped three aluminium brackets from 30mm equal angle material and reduced the 90 degrees to something close to requirement.
With those brackets in place and nearly tight I bonded the binnacle to the angle brackets. If the perishing binnacle had not slipped a bit over lunch whilst the glue set everything would have been perfect.
So, after lunch I removed the binnacle (unscrewing) the brackets that were now bonded to the binnacle, and risked everything by trying to cut through the glue to re bond the binnacle in place where it should be. 
Unfortunately the perishing thing cracked (told you so I hear you say) but not too seriously so I had to overcome that by just renewing the glue and then re attaching the binnacle using some "P" section elastomer that I had in my spares bucket.
All in all it doesn't look too bad, it has cured the rattle and I would adopt this approach again if I had another spare binnacle.

All being well attached are two images. One shows the screwdriver assemble all stuck together with gaffer tape. Yes it is resting above the arch but that was only for demonstration purposes. It was just possible with the screwdriver between the arch and the top of the instruments. 

And here is the other  

I replaced them with speed clips glued inside the rim with contact glue, the originals can cause the binnacle to split in that area.

Use of those white plastic retainers were a poor design as they inevitably crack the square holes they fit into which can spread to visible cracks along the top of the binacle

Did your windscreen reflect the p profile “rubber” insert, and if so have you found a resolution to that please?
The overall finish is a lot better than the acoustic accompaniment but the reflection is annoying.

I started with white edging but couldn't live with the reflection in the windscreen. It was replaced with some lower profile black edging which I made sure was a matte finish by a rubbing it with some 160 grade wet and dry paper. No noticeable reflections now

That explains it and sounds practical.
Another job for winter!