Substitution by Nutmeg

The completed grid contains (almost) two rows symmetrically placed, depicting a villainous man, first mentioned a little over 50 years ago, and his original setting. By changing two entries, one in each of these rows, solvers must depict a different man, more often heard than seen nowadays, and something essential to his setting. Finally a total of three letters must be erased from two separate entries to show a pair of combatants for one 11 appropriate to the final grid. Down clues each contain a misprint of one letter in the definition. The correct letters spell out a phrase which should help identification. All entries in the final grid are real words.
1    Rumbling below after this is thrown off (7)
6    Deliveries entirely welcomed by Brits on vacation (5)
10  Touching song put in new category (8)
11  Notes dispensed with in extremely rapid trial (4)
12  Georgia's back inside before sudden rise of tide (5)
13  Capital's college dons much less reliable (6)
14  Indefinable quality in timeless drink? It's rum (6)
16  Group of sailors back to back (4)
17  Standard approach such as angler may use? (7)
18  Barry's girl from Thailand possibly not accepted (4)
21  Naturally crown diminutive space movie star (9)
24  A servant ill-treated by South European royals (9)
27  Squeal, dropping set of books from among volumes returned (4)
30  My wife in Alaska trained bird (7)
33  Composer disheartened humourist (4)
34  Treatise written about "posh" beggar (6)
35  One-time premier familiarly at home, of no interest having retired (6)
36  Welcome cry once north of the border (5)
37  Forgotten path last used by James Bond (4)
38  Turkish commander aimed to relocate cold-blooded family (8)
39  Painter from back street moving to the rear (5)
40  Audible punch KO'd notorious cat lover (7)
1    Hunk in trousers preferring last of wives to first (5)
2    Rising editor cuts judges' top words for those setting the pace (7)
3    Outing I missed, injured but not pained (5)
4    Base 6ac at Lord's uncovered - two sides kept apart (6)
5    Retiming Big Ben requires adjustment (6)
6    Ashes responsible for these sounds Cook heard (5)
7    A seaman served up selection of baps (5)
8    Aliens abroad with British plugging gap (7)
9    Abandons threats (7)
15  Chic parts of Parisian hat (4)
19  Adopt conventionally produced list? Yes! (7)
20  Youngster in anguish loving knight (7)
22  Leader leaves to take in toll (4)
23  Joiner may await this plan to enhance hives (7, 2 words)
25  Almost everyone supports non-U supply of certain type of work (6)
26  Husband stops cashiers mounting Muslims' big show (6)
28  Man in Ministry mostly looks into what's bidden (5)
29  Toddler going up river bitten by bugs (5)
31  Daredevilry needed to some extent in poets' wars (5)
32  Sinned, insufficiently covered in Highland dress lacking length (5)
To enter this competition, send your entry as an image or in list format,  to before the 8th November 2015.The first correct entry drawn from the hat will receive a book from the Chambers range which has been donated by Chambers.