The Sea Harrier in this country is long gone and is not coming back WEBF. They have even dismantled (or were suppose to have done) the Ski-Ramp at Yeovilton last week. Think it's best to forget about the SHar now and look ahead.
We regularly escort US ships in theatre and they will do the same for our Navy in crisis... if you are working in a combined patrol then yes, you could rely on them otherwise there won't be any point of them being there.
Like that already said, with the F100 and Arleigh in the group, the T42 chaps must feel a little out dated.