My new replacement laptop arrived in good time and is working brilliantly. I had to upgrade to Win 10 1903 but the process was flawless unlike my experience with my very elderly laptop. Everything is good and I would recommend PC Specialist again. Years ago the desktop I bought was also excellent.
Consider doing a clean install of Windows 1903. In place upgrades can cause issues (they shouldn't, but hey..) that might not be apparent until further down the line. If it's a relatively new system and you've not installed all your stuff on it yet, a clean install could save time later