I've read the setup guides and believe I've got this right but my LAN clients cannot access the internet with a Mikrotik router I'm trying to get working on Stuff Fibre. 

I've reset the configuration on the Mikrotik. 

Used the Quick Interface Config to set the basics.

Created VLAN10 on ether1 (connected to ONT)

Configured DHCP Client on VLAN10

I can see VLAN10 is active with an external IP address and I can PING from VLAN10 to the internet using DNS names (using ping tool in winbox).

I can also resolve DNS names from the LAN. But I cannot PING or access any websites from the LAN. 

Firewall and NAT are all factory default.

Have I missed something? Everything I've read says PPPoE is not required.