LONDON — Conventional Hollywood wisdom is that it’s simply too expensive to shoot in London.

But director-producer Irwin Winkler thinks that notion of Blighty excess is due for revision. And he offers up his experience shooting MGM’s Cole Porter biopic “De-lovely,” which just wrapped production in London, as a case study of what can be done on a modest budget.

“There’s a misconception that you can’t shoot a film in London on a middle-range budget,” Winkler says. “I’m shocked that the way we’ve done this picture hasn’t been more explored.”

Winkler defines his “way” as “no elephantine studio baggage (and putting) your budget on the screen.”

Befitting a guy who watched the bottom line for other filmmakers — “We shot ‘Rocky’ in 29 days,” he recalls — he quickly crunches the key numbers on “De-lovely.”

Winkler puts the pic’s budget at “above $30 million if everyone takes their fee,” but says, “We made it for less than $30 million.

“We’re doubling everything from Arizona to Hollywood to Indiana over here in London, the U.K. and Europe, and our London base production costs are about $75,000 per day,” he says. “(But) this picture would have cost $125,000 per day in Los Angeles and $175,000 per day in New York.”

I ran Winkler’s numbers by a top indie film attorney and he concurs with Winkler’s assertions — with this proviso: “You can achieve enough savings with a period picture like ‘De-lovely’ because not having to build sets makes up for the higher London labor costs.”

Winkler also cites “the brilliant pool of acting talent, being able to get Heritage Cars, not Teamsters, to drive your people to the set and crews who might grumble about working past a lunch break but won’t bankrupt you for it.”

With the much-discussed sale and leaseback tax advantages of U.K. production, which Winkler estimates as about 15% of the pic’s budget, why are so few midrange Hollywood productions lensing in London?

The best explanation has to do with what they call in baseball “the fundamentals.”

I watched Winkler prepping a shot at London’s Cafe de Paris, which was doubling for a haunt of gay Hollywood during the Porter era, and it provided a lesson in what Winkler terms “simple, old-fashioned filmmaking.”

Winkler’s Steadicam shot would travel around the circular club space three times, each pass showing the passage of time as Porter (played by Kevin Kline) visits on different occasions. Under Winkler, the time passage was achieved not through costly special effects but by lightning-fast costume changes done off-camera.

“It’s theater magic, straight out of ‘Noises Off,’ says Winkler. “That shot, if done in post, would cost around $250,000. We did it all in-camera.

“I had in a hand in Marty’s (Scorsese’s) great opening shot in ‘Goodfellas,'” Winkler adds. “He may have covered more real estate, but this is my own answer to that shot.”

Call it moviemaking 101.

“De-lovely” — from from its frugal rights deals on Porter’s music to reduced upfront paydays for its stars and screenwriter Jay Cocks — is a throwback to a time when Hollywood filmmakers utilized European locales without mega-budgets and massive post-production trickery.

“It’s a way to make films here that almost no one seems to do anymore,” Winkler says. “Maybe they’ve forgotten how — or maybe they never learned.”