The former Netherlands coach, without a Premier League win this season and hammered 4-0 by third tier MK Dons in a League Cup match last week, signed versatile Dutch international Daley Blind for 14 million pounds ($23.25 million) from Ajax.
Rumours swirled that the move for Radamel Falcao had gone awry over a failed medical exam as the deadline closed on Monday, but the Colombian striker's one-year loan deal with an option to buy was finally announced some 90 minutes later.
"I am delighted to be joining Manchester United on loan this season," 28-year-old Falcao, who scored 11 goals in 20 appearances for AS Monaco, said on United's website (www.manutd.com).
"Manchester United is the biggest club in the world and is clearly determined to get back to the top. I am looking forward to working with Louis van Gaal and contributing to the team's success at this very exciting period in the club's history."
Last week, United broke the British transfer record in signing Angel Di Maria for 59.7 million pounds ($99.16 million) from Real Madrid and started their summer dealings with the 29 million pound ($48.17 million) capture of midfielder Ander Herrera from Athletic Bilbao.
Winless after three games in the Premier League, the rash of signings may appease the critics who have clamoured for an injection of new blood at the fallen giants.
United will recoup some of the fortune spent after selling England forward Danny Welbeck to Arsenal, while Mexico striker Javier Hernandez has also departed on a season-long loan to Real Madrid.
Arsenal did not disclose details, but British media reported the transfer fee for 26-cap England forward Welbeck at 16 million pounds.
"Everyone at Arsenal welcomes Danny to the club and looks forward to his contribution in an Arsenal shirt this season," the team said of the 23-year-old, expected to make his Gunners debut at home to Manchester City on Sept. 13.
Hernandez joins Real after spending four years at United, scoring 37 times in 102 Premier League appearances.
Blind, 24, signed a four-year deal and reunites with Van Gaal after working with the Dutchman at Ajax and the Netherlands national team.
"I am delighted Daley has signed. He is a very intelligent and versatile footballer," Van Gaal said.
"Daley is a great reader of the game, he has played under my philosophy over a number of years and he will be a great addition to the team."
Most of Europe's top sides had done their big money deals before deadline day but a host of clubs took advantage of the frenzy that usually accompanies the end of the window.
Hull City broke their club record fee in completing the signing of 24-year-old Uruguay striker Abel Hernandez from Italian club Palermo on a three-year deal, with the option of a fourth year.
The exact fee was not revealed, but Hull confirmed it was more than the 7 million pounds ($11.63 million) paid to Tottenham for Jake Livermore in June.
Hull also landed a trio of midfielders on loan - Mohamed Diame from West Ham United, Gaston Ramirez from Southampton and France midfielder Hatem Ben Arfa from Newcastle United.
Crystal Palace's new manager Neil Warnock took Scottish international James McArthur from Championship (second tier) side Wigan Athletic on a three-year deal, shortly after snapping up Tottenham reserve defender Zeki Fryers.
"Thanks Wigan for an amazing four years. They will always have a place in my heart but time for a new chapter with Crystal Palace," McArthur said on Twitter.
Newly-promoted Queens Park Rangers, whose manager Harry Redknapp is known for his extensive deadline day dealings, signed Brazilian international Sandro from Tottenham for an undisclosed fee.
The 25-year-old midfielder agreed a three-year deal, according to the QPR website (www.qpr.com).
Redknapp, who signed Sandro four years ago during his spell as manager at White Hart Lane, was delighted.
"Sandro's a proper footballer and a top class professional. He's an absolutely fantastic signing for us," Redknapp said.
"He brings energy, aggression, power and quality. They call him the Beast. He's not only a top quality footballer, but a fantastic boy as well. He'll lead by example for us."
Sandro admitted Redknapp played a key role in his decision to move across London from White Hart Lane.
"I like new challenges and this is one I'm really looking forward to. Working with Harry again, who I share a great relationship with, is very special to me," he said.
Tottenham, under new manager Mauricio Pochettino, were also active in acquiring former France under-21 international midfielder Benjamin Stambouli and loaning Lewis Holtby to Hamburg SV.
Manchester City, big spenders in the past, released England defender Micah Richards to Serie A Fiorentina on loan.
"Now there are no more doubts. The wait is over," the Italian side announced on their website (www.fiorentina.it).
They also let 29-year-old Spanish striker Alvaro Negredo, signed from Seville last year for 16.4 million pounds, leave on loan to Valencia.
Sunderland signed 26-year-old Argentine playmaker Ricky Alvarez, capped seven times for his country, from Inter Milan and Uruguay international defender Sebastian Coates from Liverpool on season-long loans.
Netherlands midfielder Marco van Ginkel, 21, left Chelsea to join AC Milan for the season on loan. He follows Fernando Torres out of Stamford Bridge, the Spanish striker joining the Italians on a two-year loan on Sunday.