We've always needed carriers ever since we invented the things and showed the Japanese how to use them at Pearl Harbour when we raided the Italian navy at Taranto and the Americans then used the idea to pay the Japanese back for it at Midway.We then scrapped the best fleet we had (which rightly used AMERICAN Phantom air superiority fighters because we had nothing at the time,or since,to match them for carrier use)during the 1970's and almost lost the Falklands war because we were using cheap cut price versions of the idea and those gutless Harriers which couldn't catch a few Skyhwaks and Etandards.
The Marines are probably happy enough to use the things because they've got the US Air Forces with 'proper' planes to call on if they get into a real fight.
The Marines use Harriers as attack aircraft, hence the US deignation as
AV-8B.
There were proposals for supersonic versions of the Harrier concept, but these went by the wayside.
The carriers that we're building now probably still won't be in the same leaugue as the Eagle and the Ark Royal of the 1970's let alone a US Navy battle group and the aircraft they carry probably won't be in the same league as a Phantom or an F14 or F18 either unless the Eurofighter can be converted for carrier use.
The replacement for the Harrier, at least in US Marine service, is to be the F-35B Joint Strike Fighter. There are 3 versions of the JSF, the A, B (the STOVL version) and C (which, IIRC, is bigger than the A or B). The F-35 program is running seriously behind schedule and over budget. IIRC one report said that it was still some 7 years away from being in production and combat ready.
Australia signed onto the F-35 program in 2002. I am not sure if we are still part of the program. I hope not.
We are in the process of buying new F-18 Super Hornets to replace our F-111s. The bulk of our fighters are the earlier, and less capable F/A-18s.
Looking at Wiki
RN Carriers the next generation carrier will have the angled deck as per US carriers. So that should allow some flexibility in choice of aircraft to operate from them.
But the Ark Royal didn't have the angled deck, and operated mainly STOVL (Harriers) and VTOL (Helicopters).
Which is why we're lucky that in most recent combat situations we've not had to rely on just recent British fighter aircraft.As for the Rotodyne,Harrier,Tornado etc as they say there's only two types of aircraft fighters and targets.The question is wether the Tornado F3 or the Eurofighter was/is a better fighter than an F15,F18 for carrier use and F22 and in which case wether the money would have been better spent on an American product.
Production of the F-22 has been stopped. It is overexpensive, not as effective as the brochure says and apparently doesn't have sufficient armour to be suitable for ground attack roles (ie apparently they are vulnerable to small arms fire!). The F-15 is not carrier capable, nor is the F-22. The Tornado isn't either, as far as I know, and I doubt that the Eurofighter Typhoon is.
The best American product for carrier-borne operations at the moment is the F-18E/F Super Hornet.
An alternative is the Dassault Rafale, which has a carrier version as well. Or, if you look to Russia there are the options of the MiG-29K (similar in size to the F-18) or the Sukhoi Su-33 (larger and more capable than the MiG, but also more expensive).
I believe the Tornado has come to or is coming to the end of its life. So it is unlikely that a carrier version of that will be possible.
By the time the RN's new carriers are completed the F-35 may be ready, so it is likely that will be the strike fighter used.