I'm not sure about other laptops, but on Lenovo yoga 500 there is a small button next to the power button which needs paper clip or similar to push. This then brings up boot menu, and I assume it will show the usb as an option if it is loaded with Windows 10 ISO.
If your computer is set to boot from the USB flash drive first, it will just keep rebooting from the flash drive. Try restarting your computer with the flash drive removed.
I have tried that and it just says no operating system installed.
The method I tried was Windows 10 - Clean Install - Windows 10 Forums
Everything is fine up to step 14 with windows restarting I do not get a step15 it just goes back to step 5 select your language.
Another update. The transfer to the SSD looks to have succeded to a degree. If I now connect the SSD to the laptop as an external USB hdd
the laptop booted up fine after asking for the key and downloading updates. If I now put it into the laptop I again get the no operating system available message. I then connected the original HDD to the laptop as a USB HDD and it will not boot. Am I missing something very obvious?
Hmmmm! Sounds like a boot order issue, where you've got multiple drives that can boot the device, and it's not clear about which device should have priority. I'd investigate BIOS settings to see what drives the BIOS recognizes, and try to solve it from that angle first. If doesn't work, please post again. Windows never fails to amaze with its infinite causes for vexation!
FWIW, I had exactly the problem you describe, and was ultimately only able to resolve it by reformatting the original boot drive (the original HDD in your post above) so that it was no longer bootable. After that, everything worked fine.
Disk Management - How to Post a Screenshot of - Windows 10 Forums
Please be sure to widen the columns so we can see all the information in them.
The SSD has a boot partition on it. Two things come to mind - the HDD is obviously a GPT partitioned disk. Is the SSD GPT or MBR? If it is MBR, it probably needs to be converted to GPT. MiniTool Partition Wizard Free is the easy way to display if it is GPT or MBR and also has a utility which might convert it to GPT. I know the diskpart command will display GPT/MBR too, but would have to wait to get home to see how to do it in diskpart. Using diskpart to convert the disk from MBR to GPT requires wiping the disk, whereas MiniTool Partition Wizard Free can do it without wiping the disk.
Second, even though the SSD contains a boot partition (EFI System), it might not have valid boot information in it. For that I would suggest either Kyhi's recovery disk (which also has MiniTool Partition Wizard on it) or a bootable Macrium Reflect Free rescue disk. Boot from Kyhi's recovery disk, with the SSD installed in the laptop and the old HDD not connected at all. Run Macrium Reflect Free, there is a utility under the Restore menu to fix Windows startup problems. That will probably put the correct boot information into the EFI System partition.
Windows 10 Recovery Tools - Bootable Rescue Disk - Windows 10 Forums