Looking to adding more RAM but cannot find compatible module

If you don't want to have memory problems, by exactly same type

Samsung 4GB DDR4 M471A5244CB0-CTD - Amazon

Samsung M471A5244CB0-CTD - Newegg.com

Thanks @

Megahertz
I have now ordered this one https://www.amazon.co.uk/gp/product/...0?ie=UTF8&th=1

scopio said:

Thanks @

Megahertz
I have now ordered this one Crucial CT8G4SFS8266 8 GB (DDR4, 2666 MT/s, PC4-21300, Single Rank x8, SODIMM, 260-Pin) Memory: Amazon.co.uk: Computers & Accessories

They are different size. You're going to mix different memory types.
They may be equivalent but are not the same brand and may have different timings.

The 4GB module would be removed.

scopio said:

The 4GB module would be removed.

You will loose double channel feature. (Only possible with two equal sticks)

Buy two 8G to have 16G (that you probably wont use)
Buy one equal to the one you already have (M471A5244CB0-CTD)
Amazon.co.uk : M471A5244CB0-CTD

The maximum GB the laptop can have is 8GB in one slot.

The laptop doesn't have two memory slots?

I don't think so or if it has I think one is disabled. I won't know until the memory module arrives and I open the laptop and try it.

If you had run HWinfo you would know how many slots you have.
2x4G is better than 1x8G as it will use dual channel (that almost double the memory speed).
And is also cheaper (£22).
It's your computer, your decision.

I will accept your suggestion and have cancelled the Crucial CT8G4SFS8266 8 GB (DDR4, 2666 MT/s, PC4-21300, Single Rank x8, SODIMM, 260-Pin) Memory: Amazon.co.uk: Computers & Accessories and ordered

Samsung M471A5244CB0-CTD Memory, 4 GB DDR4 2666 MHz

Samsung M471A5244CB0-CTD Memory, 4 GB DDR4 2666 MHz: Amazon.co.uk: Computers & Accessories

HWinfo shows that the installed module is in row two so I assume that there is a row 1?