Ever so slight and so very, very British, “The Ballad of Wallis Island” passes the time like reading P.G. Wodehouse with a cup of Earl Grey on a rainy autumn afternoon.

A couple of supporting players from British TV cooked this up and play our not-quite Jeeves and Wooster, with a woman sort of coming between them or viewed another way, summoned to give them a reason to go on.

“Alan Partridge” survivor Tim Key is a bearded, redheaded walking/punning British cliche, a shy, repressed bloke who’s won the lottery and decided what he’d really like, after buying the nicest, biggest house on tiny,windswept Wallis Island (Ramsey Island and parts of  Carmarthenshire were the filming locations), is to hear his favorite folk pop duo, McGwywer Mortimer, reunite and play one more show.

He puts up the cash and signs the contract. But he doesn’t tell the estranged pair (Tom Basden of Ricky Gervais’s “After Life,” and Carey Mulligan) or their management anything in the way of details.

The place is remote, reached only by a weathered 16 foot beach skiff. This will be no “Glastonbury.” The place’s population is low, and how they can afford a store and a phone box with almost no residents is a wonder. The show is basically for lottery winner Charles.

And neither singer/songwriter/guitarist Herb McGywer nor singer and onetime songwriter Nell Mortimer know the other will be coming. The payday will be so big his manager and her husband (Akemnji Ndifornyen) didn’t ask a lot of questions.

Imagine their shock when they wade to the beach to be greeted by the fill-the-awkwardness-with-words chatterbox Charles.

“How many people” will hear them? “Less than 100” is as specific as Charles gets. As it rains a lot, he’s inclined to be prepared himself and pointlessly note that Herb isn’t.

“You are Dame Judi. Dame Judi drenched!“

Being on the spectrum awkward has Charles hunting for puns in every sentence, often ruining them by “explaining” them as is the way of those who don’t pick up on social signals. “Let’s go, then” would never do when he can summon some twisted Shakespeare.

“Shall I plod on, MacDuff?”

Herb’s phone gets soaked and he can’t even find rice to dry it out at the tiny local story run by single mom Amanda (Sian Clifford). He needs change to use the phone, hands Charles a £50 pound note and is handed a full lack of coins.

He’s barely dried off and gotten his bearings when he realizes that it won’t be his solo work that he’s playing (he has a new album in the works) and that neither he nor Nell knew the other was coming. He won’t be able to dodge chatty/nosey Charles’ “Whom dumped or was dump by whom?” queries much longer.

When Nell shows up — she moved to Portland, Oregon after the breakup — she’s got a husband Peter in tow. We don’t have to wonder what Charles was thinking. And as Peter’s as avid birder and takes off on a puffin tour of the island, people who have and haven’t moved on will thrown together in what seems like an inevitable plot.

It’s a credit to Key, Basden and first time feature director James Griffiths that the story trips up expectations at most every turn, often to comical and charming effect.

Charles has a grass tennis court and a shockingly good serve, Herb discovers. But as the jackpot winner hasn’t had anyone’s serve to return in eons, their match is sure to be deadlocked.

In fleshing out a short film they made with these characters and this story back in 2007, Basden, Key and Griffiths reach for deeper hurt and fuller explanations of the how and why everyone is like they are. Mulligan signed on and made the film plausible, in terms of star power finances. But what all involved were hired to do was to underplay their characters. They explore the infamous British reserve, where so much is left unsaid, suffering in silence is a national sport and punning a birthright obligation, and do it all in a “Jane Eyre/Wuthering Heights” setting.

The songs are pleasant enough, with Basden a convincing troubador and Mulligan not bad at all at harmonizing. But this isn’t “Once.” “Pleasant enough” carries a lot of baggage in describing the tunes. There’s not much here that would seem to merit obsessive fandom.

That said, the performances are spot on. And all involved have made a marvelously melancholy “feel good” movie that ticks off so many Brit film boxes — eccentric characters, quaint and soggy setting, emotions kept under wraps and a charming, wistful story about moving on, being smart enough to realize the need for it and kind enough to help others manage it as well.

Rating: PG-13, smoking, profanity

Cast: Tom Basden, Tim Key, Sian Clifford,
Akemnji Ndifornyen and Carey Mulligan,

Credits: Directed by James Griffiths, scripted by Tom Basden and Tim Key. A Focus Features release now on Amazon Prime.

Running time: 1:38