They are clearly in the wrong and hoping that you will just give up and go away.
Inform them in writing, ideally email, that they have failed to repair the product and you expect a refund within seven days. If the seven days elapse then file a case with the Disputes Tribunal.
The laptop may not have been faulty at all. Everyone is just assuming .
1/2 hour to startup , yeah, can happen after updates. Ive seen much longer
Slow , yeah 10 does slow down when when downloading major version updates , especially on low spec machines . Got one here now, real speed issues
as it tried to deal with failing updates.
Shutting down when playing movie :yeah, win used to be famous for restarting unexpectedly to install updates. It happens.
If it was constantly restarting , then yes that would be an an issue. Once , pfft.
Even new laptops often need to be de-crapified . Manufacturers pre-load so much bloat. I often need to spend 1/2
hour AT LEAST cleaning up new laptops I sell . Add to that they usually come with old versions of Win10, sometimes very old builds: so
old that they will no longer update properly.
Whats the spec of the laptop. If its underspeced or just slooow in general (some really are) that doesnt make it faulty
As the the possible charge for repairs.
Thats normal. If deemed to be a non waranty issue (ie software or OS), some repair agents will charge for that work
The 'repair' will be sent out to 3rd party that does repair work for Acer (or is done in house). If it isnt a warranty issue, Acer wont pay the repairer, so the customer gets charged . (I used to do Acer warrnty repairs many years back, awefull awefull work)
That reason for POSSIBLE charges should have been explained to him much better I'd admit.