Seems there is (was ?) also a shortage of qualified crew. Since 2015 the French Marine Nationale (hereditary enemy!) has even loaned some personnel for British warships.
Here is a 2016 (+ update) article on the French Defence(Navy) website:
The English translation is:
Five years after the signing of the Lancaster House agreements, cooperation with the Royal Navy has taken on a new dimension this year(2016) with the posting of three Senior Maritime Officers (SMOs) to the British Navy. Although there are regular exchanges of officers, this is the first time that SMOs have been integrated into British crews. The Royal Navy, which is plagued by a shortage of technicians at the higher certificate level, can now count on the support of the French Navy!
The Chief Petty Officers (CPO) H., L. and Petty Officer (PO) R. were all selected for overseas posting. They left Brest and Toulon for Plymouth. On the programme of this new type of exchange: 10 weeks of training in English, technical training to understand the specificities of Royal Navy equipment, followed by 2 years on board a frigate or amphibious vessel as sector leader.
10 weeks. This period is not too long for those who will soon be working and living on board a British ship, fully occupying a position and leading a team. The three men thus followed one course after another, covering all aspects of their future duties, even the most unexpected ones such as writing a report card in English! Another aspect of these 10 weeks was understanding and mastering the "Jack-Speak", the jargon of the Royal Navy, as well as its habits and customs. It's no small task, but the Royal Navy's welcome has been particularly warm. Invited to celebrate Pickle Night(1), the French sailors were even able to discover the celebrations associated with the Battle of Trafalgar from the inside.
(1)The HMS Pickle is a schooner that took part in the Battle of Trafalgar. Weakly armed, she did not take part in the fighting but rescued many wounded and brought the news of victory to Great Britain on 4 November 1805.
Armed for the continuation of their exchange, they are now undergoing technical training specific to their future assignments.
PM H. is posted on the frigate HMS Monmouth as head of the electrical production/distribution sector ;
CPO L. joins HMS Ocean, Royal Navy Flag Ship, in charge of the barge sector;
DTM R. is the Chippy (2) on the frigate HMS Somerset, in charge of the hull installations and auxiliaries.
The integration of the French sailors has also gone through the gates of the dockyard, as two of them have settled down with their families. Benefiting from the Navy's support for accommodation and school enrolment, they discovered and appreciated the British way of life and came to enlarge the "French military community of Devon", which grew from two to five representatives!
These first three exchanges of naval officers will continue next year with the arrival of a new group. The presence of naval officers on board operational units of the Royal Navy thus broadens cooperation and underlines the dynamism of our relationship and the mutual trust between the two navies, the main European players on the seas.
(2)The Chippy is historically the ship's carpenter. Today, he appoints the head of the sector in charge of hull installations and auxiliaries.
Two new permanent berths at sea are also in place since summer 2015. One for a Chief of Watch, the second for an Operations Watch Officer. Ensign (EV) Genty has joined HMS Kent. Fully integrated into the crew, he performs not only his duties as Watch Commander, but also those of Company Captain and Watchkeeping Officer. LV Dhellemmes is currently taking the Senior Warfare Officer course before being posted on an English vessel as Operations Watch Officer.
Sir Horatio, please come back: the new world has got insane