While the cast and writers of “Saturday Night Live U.K.” are front and center of the British adaptation, the show’s secret sauce is, of course, the artisans. From hand-sewing individual strands of hair onto a David Attenborough wig to tailoring the perfect Melania Trump suit, costume, make up and hair teams are “SNL U.K.’s” unsung heroes. Kevin Fortune heads up hair and make-up (the team also provide prosthetics when needed), which numbers between 14 to 18 people depending on the day of the week, while Annie Hardinge leads the costume department, which is comprised of around 6 costume assistants. Their week begins on Tuesday, when they meet the celebrity guest host (which so far has included Tina Fey, Jamie Dornan and Hannah Waddingham among others) and shoot a promo for the coming Saturday’s episode (for the season finale this week “Doctor Who” star Ncuti Gatwa is on hosting duties).…