I have installed Mint 20.2 OK. However the latest Ubuntu addition, whilst working does not seem to be installed correctely

And the question is?? Do you have any particular reason to believe it was not installed correctly? Do you get warning/error messages? If so, what are they?

What is the latest Ubuntu addition? I'm guessing something different than the arithmetic we're all used to...

If it runs, it is properly installed.
The issues you may be encountering are likely directly related to the quote below.
There's another 350 or so active Linux, around a thousand altogether and many variations of Ubuntu.
There's a good chance you can find something that installs better.
Mint and Ubuntu are two peas from the same pod.

Sorry I was not precise in my question,I will try again!

When I Select Mint, there is an immediate response. When I select Ubuntu, there is a large page of errors flashed up quoting errors ( concerning boot and bios etc). To quick for me to note. I have obviously made a setting error, but works OK. I must admit I am very much a novice.
Thank you so much for your quick replies,

You might try looking at the logs on Ubuntu after booting, particularly relating to booting. The link below gives a description of what various logs to check for different problems.

https://stackify.com/linux-logs/

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There are some generic errors I've seen on my hardware that are common amongst most Linux, some related to ACPI that the word on the web is to not worry about it, the open source Nvidia driver called nouveau tends to be fussy also (boot time errors) but works nice.
Many errors are results of early probes into hardware configuration where later in the boot process it get's set up properly as such the error is misleading.

With Ubuntu there is a 3rd party software app that will suggest installation of proprietary drivers if needed, this may take some errors away.
It's terminal has great color scheme helping point out issues making it easy to find them if you are not fluent in Linux when running command ---> sudo dmesg | less
And command ---> sudo journalctl -b will show more or less the same but more detailed, this will show all events during the last boot.

EDIT: Also, you can search for patterns in those commands, to search for the word "error":

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