You need these three files all in the same folder:

setup_the_witcher3_exp2_2.0.0.45.exe
setup_the_witcher3_exp2_2.0.0.45-1.bin
setup_the_witcher3_exp2_2.0.0.45-2.bin

You double click on the .exe file. You do not need to touch the .bin files. Remember, they MUST all be in the same folder, and you must have full access rights.

So I must copy all three downloads into Gog games/ The Witcher folder then run the .exe file?

UPDATE: I did this but it cannot find the file with "language pack" in its title. I only downloaded the three files you quoted and did not think that I also needed to install the other three believing them to be for languages other than English.

ANOTHER UPDATE: The .exe file only had Blood and Wine- lang- pack in title.
I deleted it and downloaded the exact file as listed in available downloads and this time it is correct.
Only the last three files on the list relates to language packs and I did not download any of them. Weird to say the least.
I still can not install as I apparently require patch no.1.2.

Yes, this is required for Blood and Wine.

All that is available in Gog downloads is patch 1.22 part 1 and 2.
Do I need both these do the job?

Ok, this isn't getting us anywhere. Here is what you should do, so that no errors are made:

First, download these files from your account, and place them ALL in a temporary folder. I suggest C:\Downloads\TW3\

TW3 1.10 main installer (files 1 to 8)
Patch 1.22 (files 1 to 2)
Free DLC 1.22
Hearts of Stone 1.22 (files 1 to 3)
Blood and Wine 1.22 (files 1.to 3)

You do NOT need the multi-language pack if you play the game in English

Now, uninstall the game from Control Panel. Keep your saved games when it asks.

Now to reinstall the game. Run the setup files in this order (remember you ONLY need to click the .exe files):

setup_the_witcher_3_wild_hunt_2.0.0.40.exe

WAIT for it to finish installing, it can take a long time, Be patient.

patch_witcher3_1.10-1.22_2.0.0.45.exe

WAIT for it to finish installing.

setup_the_witcher3_dlc1-16_2.0.0.45.exe

WAIT for it to finish installing.

setup_the_witcher3_exp1_2.0.0.45.exe

WAIT for it to finish installing.

setup_the_witcher3_exp2_2.0.0.45.exe

WAIT for it to finish installing.

Once the final one is finished, your game is clean and fully up to date.

All this is quite intimidating for my ancient brain. Anyway I in stalled patch 1.22 then Blood and Wine installed successfully.
I launched the game but have not yet started playing. Thanks for you input anyway.

btw: my Blood and wine setup package (setup_the_witcher3_exp2_2.0.0.45.exe ... *1.bin *2.bin) has a wrong title by mistake of the compiler - Its called voice overs when you run it - but its the base setup required in first place before you install the (non uk) additional language pack