Just booked a crossing with P'nO Dover/Calais for July. Total length of tow and trailer is about 50' and somewhat tall. Travelling in the wee small hours took the price down from £350 each way
to £90 each way
... so use their website diligently..
Get the trailer bearings changed, tyres checked and brakes overhauled…. not a lot to go wrong with a trailer.
<edit>..like what Pete7 said..AA will recover vehicle, but not trailer, but they will recover vehicle and tow trailer.. does that make sense? At least that’s what my insurance policy offers.. give ‘em a call.