Ok have just updated the firmware to .600 on my new 2021 October version (previous was Nov 2021), during that time in my bedroom there was no GPS for it to lock on.
Once all updated, I went out to the back garden and powered it on. It took roughly 1min 10sec to acquire enough Satellites to stamp the Home Point. It then hung at 13 Sats for about 3 min longer then jumped to 14. It took the whole 5min to reach 15 Sats. Not sure how many Sats I should be seeing locked on normally after 5min?
I powered it off, then back on again after 1 min and it immediately fixed at 14 and the home point was recorded.
I will again try this tomorrow morning or later on a cold start while out.