Since 1 April new EU rules mean that Netflix should allow you to watch UK content while you are in Crete BUT it will probably be time limited. It is really intended to allow citizens to watch content from their own country while they are on holiday in another EU country not to provide a permanent service in that other country. I think Sky are limiting it to 1 month but I am not sure about Netflix.
If you want to watch long term then you will certainly need a VPN and you may find that Netflix search out VPN IP addresses and block them. You may lose contact for a period, while the VPN provider changes their IP address, or you may need to change VPN provider. Not all VPNs work with Netflix so make sure you choose one that does.
After 29 March 2019, when the UK leaves the EU, Netflix have announced that they will stop the provision to other EU countries and so everyone will need a VPN to access Netflix UK even if they are only in Crete for a short time.