Passing 2 miles off Dover harbour, while bound for Le Havre, a UK ship finds a floating liferaft and manages to recover it on board. Should it be landed at Le Havre?

No.

Under the Merchant Shipping Act 1995 it is an offense to take into a foreign port and sell: (1) any vessel stranded, derelict or otherwise in distress found on or near the coasts of the UK or any tidal water within UK waters; (2) any part of the cargo or equipment of, or anything belonging to, such a vessel; or (3) any wreck found within those waters.