Good luck with keeping the drill holes exactly where they should be. And take those bleeding labels off (what is it with labels and their nigh impossibility to remove?!!)
Dex, what I will do is pilot with a small masonry bit first before using Big Bertha.
Of course. Must admit that if it were me, I’d tack the fence panels in place as well as those uprights into the sockets first. Wouldn’t want to be putting any undue stress on the sockets when one discovers that the best laid plans don’t always work out after all 
The grinder made light work through the concrete post.
https://i.ibb.co/JvD3kmH/4-DB9-AE3-D-3234-452-B-9680-64-D868-C94922.jpg
Big Bertha made light work of the holes.
https://i.ibb.co/fq3G2mf/2-AA78-E2-A-10-B4-4129-AD4-D-EAD20-B0420-E6.jpg
My long extension lead has gone up the wall, off to sort that now so I can drill and plug the post at the top of the garden.
Typical.
Had the same kango as you for many years until it got nicked.
Also had a 9" angle grinder until, out of the blue, I lost my bottle:blush:
Yes Dex, on the Vine programme a couple of years ago, there was an item on DIY accidents, there was a geezer on there who had a grinding disc break, a chunk embedding its self in his groin, so thoughts are never far from my mind.
One concrete sump fived to another (I forgot I had a spare extension)
https://i.ibb.co/Wxq1Vw7/D0715066-8-A10-45-AF-8133-2186-F8-F65640.jpg
Had to work out what “sump fived” meant. Thought it was a technical term before I saw the typo’s:lol::lol:
Anyway - that’s the easy one done…
This photo should give the final explanation, the timber at the bottom is the same length as a gravel board, the wooden post is 100X100mm, 25x25mm piece of timber will be screwed to the far side of the post, the gravel board and panel will be inserted, then another 25X25mm timber screwed to the front of the post making a wooden slotted post so panels are removable for maintenance etc.
https://i.ibb.co/BG8FrKn/449-D7246-F195-4145-99-D2-4-E21420-D35-C0.jpg
They are just techo “Buzzwords”.
Should work just fine. In theory, anyway 
What has happened is, the slab is 3.8 metres wide, and a panel is 1.8 metres, so two panels = 3.6 metres and the recessed centres of a slotted post = 55mm a total of just over 3.7 metres. In reality the concrete post just fitted is setting the start distance by 80mm (55mm for the solid centre bit and 25mm for the slot the side nearest the existing post), then the wooden post is 100mm without any slot so, the extra dimensions will have the effect of moving the second wooden post halfway over the edge of the slab, giving two options, extend the slab and fit stock gravel boards and panels or fit post equi-distance on the slab and shorten gravel boards and panels, methinks that is a better option.
Trimming panels is fairly easy (although you’ll come to hate the nails the manufacturers use:lol:). Just be careful - unless you’ve measured already - a panel is 6ft which is about 1.83m. That 3 cm can make all the difference;-)
I noticed that today Dex, I had the panel out to the right of the concrete post to give it a coat of preservative, whilst out i used the panel as a template for the timber on the floor, I’ve cocked up a few things referring to a measuring tape.
Assumptions make a monkey of us all Spitty.
Asked my brother to knock up the studwork for a wall which would be covered by 6 by 3 plasterboard panels. Naturally assumed that he’d know that the panels were actually 1800 by 900 mm, as he’s older than me and done some boarding himself in the past.
Apparently not:shock:
Noggins in wrong place as well as a few uprights. Easily managed to change things and work to what he’d built, but was time wasted.
He also has a thing about using nails instead of screws, which would have made things easier to adapt. Did warn him about it, but he’s not a man to take advice.
I never use nails Dex, I like to know things can be de-constructed without damage. I went with option one with the fence, couldn’t be arsed customising the panels and gravel boards, the extra concrete slab will replace one of the slabs when finished.
https://i.ibb.co/B4sY8L2/43-D0-A9-D0-9-B57-415-B-856-F-702-EC114125-B.jpg
This is the concept.
https://i.ibb.co/GtmXRjc/C7-A047-DB-56-BD-4-FAD-B377-9-CEFA2-E685-FC.jpg
Makes sense.
This will be the fixing point for the second plate, I won’t fix it for another 24 hours till the concrete is well set.
https://i.ibb.co/gmwzK5x/2832-D495-8-D1-F-4-F17-B108-7-F276-C46-BFF8.jpg
Personally, I’d leave it for a few days before drilling into it. Less chance of a catastrophic crack.