Riain, on the one hand you "asked" "to see if it's possible" (that Britain can be "saved", whatever that means). On the other hand you are already very certain that Britain was so "stupid for prematurely abandoning its own capabilities", meaning that you think you already know what it would have taken to "save" Britain. Nothing unusual for alternate history, which has often to do with wish fulfillment, but not exactly logical.
Now what exactly do you mean by "client"? "Client" can be just another word for "customer". But the words "client state" mean something entirely different, a state that is de facto, but in most cases not officially, ruled by another state, as the wikipedia article mentioned explained. Typical examples are Egypt and Iraq after 1922 as British client states, or the princely states in India. East Germany might also be called a Soviet client state.
Now what do you mean by Britain "to become a client/partner itself" ?
Do you mean that British individuals, British firms and the British government are clients in the meaning of "customers" of foreign firms? Well, individuals, firms and governments in every country of the globe buy from foreign firms, and if there are any exceptions to this statement at all, they must referr to the very poorest countries on earth.
Or do you think that Britain has become a client state of the USA? I very much doubt that it is, but if you think this is true, because Britain is less powerful than the USA, well then, all other countries are client states of the USA, and this state of affairs will only change if some other country replaces the USA as the most powerful nation.
Now what is it?
I think it Britain was stupid to lose such an advanced industry when they had the leading edge over the compatitors with the new wave of propulsion. However even if the British aviation industry goes from strength to strength the other industries could go down the shitter. My first and second cars were Minis, which was an awesome design in 1959 and throughout the 60s but by 1974 and 1976 they were long in the tooth and in particular their engine design was shit. I thought that maybe if advanced engineering and the like was as common as muck in Britian due to their world leading aerospace industry maybe the 1974 Mini could have a canted-valve alloy head and roller valve-gear or something.
I deliberately use the term client state because buying advanced military hardware is a result of a relationship, which is why Australia buys so much stuff from the US, but still goes to Europe for stuff and never to Russia. A sale of British fighters is just as likely to lead to the sale of British transport aircraft, helicopters, tanks, APC, warships and the setting up of British facilities in the host country to maintain all this shit and lead to port and airfield access agreements and the like. So by selling the transonic Hunter in the Mid East Britain is likely to sell all sorts of crap and get other benefits, just like the USA does all over the world.