Boat transport is a haulage problem with a fragile, oddly shaped load. For anything up to roughly 2.5m beam and a few tonnes, it is a straightforward trailer job on a standard commercial outfit. Beyond that you enter abnormal-load territory: over-width movements need Highways England and police notification, an escort, sometimes a night run, and a route survey for bridges, roundabouts and low branches. A 4.5m-beam motor cruiser is a different job altogether, with its own permit, its own trailer and its own price.
The mechanics matter as much as the permits. The boat has to be cradled or chocked to support the hull where it is designed to be supported, which on a fin-keel yacht means the keel taking the weight and the pads only steadying her. Get that wrong and you distort the hull or crack a bulkhead in transit. Masts come down and travel separately or lashed along the deck; propellers, radar arches, davits and biminis often come off; and the lift on and off at each end has to be booked with a yard hoist or crane that can take the tonnage.
The alternative is a delivery skipper taking her round by sea, which is usually cheaper on long coastal legs but weather-dependent and adds engine hours. Most owners compare both, particularly for a purchase that has to move between UK coasts.