boot problem since last upfrade 20.04.3

[Grizzly]

Hi all

Not sure what exactly happened

I was running 20.04.3 Kernel 5.8.0-59 Generic with no problems (AFAICT)
nvidia-340 driver been used

I ran 
sudo apt update && sudo apt dist-upgrade

I thought I had reboote dto chack all wen twell (I normally put
&& shutdown now -r
on end of cmd)

When I tried to boot today it goes to a blank black screen with a flashing 
curser some times (but all the time) I left it for 30 mintues with no change 
shutdown (Ctrl+Alt+Del)

booted into "Advanced Options" recovery
lsb_release & uname gave
20.04.3 Kernel 5.11.0-27 Generic

ran
apt update 
apt dist-upgrade
shutdown -r

When I tried to boot it went to a blank black screen with a flashing curser 
some times (but all the time) then odd vertical coloured lines / horizontal 
coloured bands an bac to the curser 

I left it for 30 mintues with no change 
shutdown (Ctrl+Alt+Del)

booted into "Advanced Options" recovery again

lsb_release & uname gave
20.04.3 Kernel 5.11.0-34 Generic

any ideas short of sticking with 5.8.0-59 ??