So I have done a bit more research and have resolved this so thought I would share: I added a python script to /etc/network/if-up.d/ as per below (need to run chmod +x ‘filename’ on if after writing it using vi or some other editor:
#Exit if network device "tailscale0" exists
ip link show dev tailscale0 >/dev/null 2>&1 exit 0
#Exit if we are not starting "eth0"
[ "$IFACE"='eth0' ] || exit 0
/opt/tailscale_1.14.0_arm/tailscaled --state=tailscaled.state &
#Provided time for tailscale to startup before attempting to authenticate
sleep 5
/opt/tailscle_1.14.0_arm/tailscale up -authkey tskey-XXXXXXXXXXXXX
I am also going to follow the following post to place the auth key in an encrypted folder
Anyway, happy to hear any feedback/improvements, hopefully it makes someones elses life easier