Port-to-port is the bare-bones service: we load the vehicle at the UK port and deliver to the destination port. You handle UK collection (driving to the port) and destination delivery (collecting from the port).
Door-to-port adds UK collection. We pick the vehicle up from your address on a transporter and deliver it to the port for loading. The destination collection is still on you.
Door-to-door is the full service. We collect from your UK address, ship, clear customs at destination, and deliver to your destination address. The most expensive option but the least hassle — and the right choice if you're not at the destination to collect personally.
Cost difference: door-to-door typically adds £200–£600 depending on inland distances at both ends.