[OzXFR]

I think it's just easier when the head is bolted down. I don't think they wanted to replace the injectors, but now they are forced to.

Yep.
It's apparent that those injectors are usually stuck incredibly hard so removing the head and getting them out from the front using the removal tool would be extremely difficult if not impossible. How do you hold the head without special tools and/or damaging it?
You need to remember these bloke were looking to get a good working RR on the cheap so of course they tried the simple fixes first.

 

[OzXFR]

Surely all the Jag petrols were designed and mapped to run on rubbish low octane fuel considering that so many of them are sold in the US so as you say the stock AJ133 most probably isn't configured to really make use of 98. I guess that's one of the reasons to why they (and above all the supercharged ones) all have some room for improvement through a remap. After remapping mine performs best with 98 or better and I can feel a small difference in low end torque between 95 and 98.

All Jag petrols from at least 2009 onwards eg the AJ133 and AJ126 were designed to run on a minimum of 95 RON (91 AKI in the good ol' US of A). Dunno about the 4.2 V8 or the Ingenium 4 potter but I suspect it is the same.
I don't feed mine anything less than 98 RON especially as it has been tuned but I believe it would run perfectly OK on 95 RON but maybe a little down on max power. Also JLR say the later Jag motors all should be fed no higher percentage of ethanol than 10%.

 

[OzXFR]

I had to look it up, it seems that the engine was developed by Jaguar by their people, but they pretty much just leased space within the Ford factory, perhaps explaining the confusion?

Yep, lots of confusion.
Many of our American friends think it is a Ford engine but they are dead wrong.
It was designed in 2008 a few months before JLR was sold by Ford to TATA, so still under Ford ownership at the time.
But it was almost all JLR engineers involved with maybe a bit of Ford input.
Much of the confusion arises because many of the ancillary parts are stamped "FoMoCo" (such as the timing chain tensioners featured in the vid), but that is only because the engine is (and always has been) built at the Ford engine plant in Bridgend, in a separate area set aside for this engine (and the AJ126 V6) under a long term contract with Ford. It makes economic sense to use some Ford parts, but absolutely none of the basic engine parts are shared with or used in any other engines. The contract is set to expire in December this year but who knows it might be extended!

 

[OzXFR]

Why did they need to take the injectors out and if they needed to, why didn’t they attempt it when then heads were off instead of struggling in situ?

They already knew that the valves on the LHS bank were stuffed and possibly the pistons as well (it so far has turned out that the pistons may be repairable), so the head had to come off. Once the head is taken off it needs to be checked for damage and possibly honed, and to do this the injectors must be removed.
If the injectors are still OK and not damaged beyond repair in theory it is much easier to get them out in situ (leave the head on) using the special JLR injector removal tool.
Our friends tried this twice, using two different (but identical) tools, but still some of those damn injectors would not budge. They were stuck super tight due to burnt on carbon deposits, a common thing on higher mileage AJ133s (and 126s) which has been reported many times on the Yank forum. At least one case reported there of an injector being stuck so tight that wrapping a chain around the injector removal tool and winching it up lifted the whole car off the ground and still the injector would not budge!
So they were forced to take the LHS head off with the three stuck injectors in place and send that head off for repair.
When they tried to get the injectors out of the RHS head the rearmost one would not budge and it eventually broke off.
So that head had to come off as well to get the broken injector out, and they did so by punching it out from the back side.
Putting all that together, yes they could have simply pulled the heads off and punched out all the injectors from the back sides. But that will always destroy the injector(s) and new ones ain't cheap (and they only come as matched sets of four), let alone the labour and parts cost of removing the head(s). Muuuuuuch cheaper if the injectors can be removed in situ with the special tool, cleaned up and refitted!

 

[OzXFR]

So was it the dealer who fudged it, or was it a DIY mistake?

Interesting and informative vid.
But why oh why does the presenter make the same old stooopid error? Not just once but twice.
At one point he says the bags of new valves are Ford valves. Noooooooo!
Then near the end he says it is a Ford engine. Double Noooooooooooo!
I would have hoped his mate who knows a helluva lot about working on the AJ133 would have corrected him but obviously that never happened.