We’ve got external insulation so it’s the right version of the bracket for us.

That looks to be the version of the Vaillant bracket for walls with external insulation.
It uses 68mm discs to pass the bolt through the outer insulation layer.

The bolt itself is 'glued' to the solid wall beyond the insulation layer using the Hilti HIT-HY-170 chemical anchor.
It's a resin and hardener compound which gets mixed by the flutes on the inside of the nozzle as it gets injected into a pre-drilled hole.

The downside of your installation seems to be the gap left around the 20mm corrugated-plastic conduit which supplies the electricity.
That will need sealing with a low-modulus mastic to prevent ingress of rain.

There are two gauges.
The thicker one is about 5mm, which means I have to use a vice and lump-hammer to re-form the angles.

Alternatively, in these far-western realms of England, we still have blacksmiths who will create whatever you wish for 😀 

Good to know it can be done without needed ex pensive plumber and spark back to extend wiring and lines. Could not sleep in bedroom it's currently attached to when running in winter.

Most people don't bolt them down...
.... whilst a few put a bolt straight through the steel channel and the rubber mass, then into the concrete pad below
which somewhat defeats the whole point of its vibration absorbing properties! 🤨 

If you look closely, there's a recess along each side of the foot.
That's the location where it can be held.

Either drill a hole and insert a long bolt at an angle (as shown in purple),
or else use a steel angle (orange) and a vertical bolt (blue).

The easier route is to buy anti-vibration feet from BES, which are similar to those shown in @toodles ' photo.

There are different patterns and lengths. The link above takes you to one with a 400mm integral steel C-channel.

With a bit of thought you should be able to reposition the unit without having to call out a heating engineer.
Remove the drip-tray and have a look at the underside.
You might be able to raise it 1cm on a couple of car-jacks if you spread the weight via a piece of plywood or some old floorboard.

Once you've taken the weights off the existing shock-mounts, they should be easy to unbolt.
Likewise the wall-mount-frame can then be removed.

Slide in the new anti-vibration feet, fit T-nuts and bolts, then lower the unit onto the new concrete pad.
Get the T-nuts from the same supplier as the feet, so you know they'll fit.

Two things to watch out for:

1: Take precautions to prevent the ASHP toppling forward or back when you lift it.

If I was doing it, I'd put a couple of ring-bolts into the wall about half-way up.
That allows me to use nylon rope to stop it moving forward.

Add some soft cushioning behind to prevent it falling backwards against the wall.
I'd probably use some pieces of Celotex or Kingspan rigid insulation board.
Then tighten the nylon rope to squeeze the ASHP against that cushioning block.

2: The easier you are able to lift the unit with car-jacks, the easier it is for a gang to steal it using a trolley jack.

When you construct the concrete base, make it as difficult as you can for them to slide their trolley jack below it!

When you remove the temporary nylon rope, you might be able to use chain or stainless-steel hawser on those two ring-bolts.
You need to find a secure way of fixing that to the back of the heat pump without damaging it.
There are 'security bolts' available, which are easy to fit but tricky to undo again.

Thieves will arrive with a bolt cutter to chop through the pipes and the electric cable anyway.
So you need a bit of thought as to how a chain or hawser can be attached to make access difficult.

There are several suppliers of stainless 'rope' in the UK, such as GS Products.
They also offer all sorts of loops, shackles and fixings, and should be able to advise you of an effective deterrent.

Cheers  for info, where I live I don't need worry about someone robbing my heat pump.