Suggestion – do not give £150 million to the French to stop the inflatables.
Have teams of British ‘bird watchers’ who are given a paid holiday on the French coast armed with binoculars (day and night), a mobile phone, a SatNav and a book of seabirds. They saunter along the coast ‘watching birds’. If they happen to spot a dinghy they phone a control centre in the UK giving the satnav coordinates who then contact the French police. All very immediate.
Every couple of weeks or so the ‘birdwatchers’ are replaced with another group of ‘birdwatchers’.
However the people traffickers are usually armed and very dangerous. It may be better to send the SAS in mufti.