Thank you for your information guys. I am now considering ordering the London Rail Atlas (5th edition) as well as the Rail Atlas of Great Britain and Ireland (15th edition). Given the latter of the two will be in stock from 2019 and that I live outside the UK, would it be alright to order them off Amazon? I would basically receive the London one and the other one in 2019, when it will be in stock.
Later edit: I ended up ordering from Book Depository the two I mentioned above and also the 2019 EMUs, DMUs, Locos, Coaches Pocket Books and the UK Metro and Light Rail Systems book. Looking forward to receiving them as I always enjoy the railway system and the rolling stock in the UK.