Donington also insists the work would not affect next year's MotoGP race at the circuit.
The 250cc category is now called Moto2, while the top level MotoGP is 500cc.
McWilliams is the last British rider to win at MotoGP, at the 2001 250cc Dutch TT.
BBC: SPORT | Motorsport | Motorbikes | McWilliams delays MotoGP decision
The 17-round MotoGP World Championship starts with the Spanish Grand Prix at Jerez on March 26.
BBC: SPORT | Motorsport | Motorbikes | McWilliams delays MotoGP decision
The MotoGP World Championship now moves to Barcelona for next week's Catalan Grand Prix.
The problem has caused the postponement of the MotoGP race scheduled for Motegi in Japan next weekend.
John Hopkins claimed his first MotoGP pole after beating Shinya Nakano's time at the end of qualifying.
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McWilliams had just one MotoGP ride last season for the KR team at Brno, in the Czech Republic.
BBC: SPORT | Motorsport | Motorbikes | McWilliams delays MotoGP decision
Splitting the sessions will also give the sponsors of smaller teams more television exposure, the MotoGP website said.
CNN: Rookie Marquez outshines MotoGP champion Lorenzo in Qatar
This persuaded Suzuki to give him a chance in MotoGP, and Hopkins has noticed his impact straight away.
BBC: SPORT | Motorsport | Motorbikes | Fired-up Hopkins raring to start
Rossi is just a point behind with Qatar MotoGP winner Stoner in third with 38 after two races.
But seven-time champion Rossi has stayed loyal to MotoGP and will return to Yamaha for the 2013 season.
It shows that Bradley, Scott and Danny are all in the right place to develop their MotoGP careers.
BBC: SPORT | Motorsport | Motorbikes | MotoGP's Sunday night fever
The problems have also led to the postponement of next Saturday's Japanese MotoGP.
Toni is one of the nicest guys you could meet and it proved to be his only win in MotoGP.
Four British riders started the 2004 MotoGP season but none are guaranteed a place in motorcycling's elite for next year.
BBC: Shane Byrne says his MotoGP future is still not sorted out.
More importantly the Honda rider now goes one point clear of his nearest rival after winning last week's Spanish MotoGP.
"At the end of this month in Herez I'll be testing the MotoGP bike with Suter, " Redding told BBC Radio Gloucestershire.
Porto has won seven races and finished on the podium 19 times since his debut at the Argentine MotoGP in 1994.
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Earlier this year film star Antonio Banderas supported a MotoGP team but it has recently collapsed after its major sponsor pulled out.
After an injury-plagued season with Stobart Honda in British Superbikes, McWilliams, 41, has been named on the 2006 provisional MotoGP entry list.
BBC: SPORT | Motorsport | Motorbikes | McWilliams delays MotoGP decision
In his three previous MotoGP campaigns - one with Yamaha and two with Suzuki - Hopkins has finished 15th, 17th and 16th.
BBC: SPORT | Motorsport | Motorbikes | Fired-up Hopkins raring to start
It is a welcome upturn for Davies, who lost his place in MotoGP when he was dropped by Campetella Racing in June.
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World Superbike champion Toseland, also in his first MotoGP season, was not content with his placing, despite never having ridden the circuit before.
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Honda's Stoner and Pedrosa have won the last two Indianapolis races, and both are seeking to cut Lorenzo's lead following MotoGP's midseason break.
The MotoGP circus moves to France in two weeks time for the fourth race of the season at the famous Le Mans track.
British rider James Toseland equaled his best finish in MotoGP when he claimed sixth for Edwards' team after Italian Marco Melandri crashed late on.
Like a MotoGP bike it has an all carbon fiber unified frame and bodywork that weighs less than 25kg and even rolls on carbon wheels.
ENGADGET: Roskva electric motorcycle revealed in Norway with carbon fiber chassis and clothes
Mobilityland Corporation, the Japanese operator of the Motegi venue, north of Tokyo, said it hoped MotoGP fans could attend the event later in the season.
Hayden's first-ever MotoGP win in Europe stretched his championship lead to 42 points and really puts him in pole position to dethrone Yamaha's Valentino Rossi.
BBC: SPORT | Motorsport | Motorbikes | All to play for in MotoGP
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