EDF Energy has made the deals despite the UK government reviewing the plans and not yet giving final approval for the nuclear plant.
The French firm said it was "highly positive" the plant would be built.
Those opposed to the nuclear build said EDF was attempting to "twist" the arm of the government.
More on the Hinkley contracts and other news from the West
Earlier this month EDF agreed to invest in the first new UK nuclear plant in 20 years, and was poised to exchange contracts with the government.
But hours after the decision was announced by the French energy firm, the government said it would review the plans and make its decision in the autumn.
Roy Pumfrey, of the campaign group Stop Hinkley, said: "They're trying to bounce the British government into not having a pause, but perhaps even having the Prime Minister returning from holiday in Switzerland to say, 'All right, we'll give in, we'll go ahead with it'.
"I cannot believe the British government is going to have its arm twisted by them. "Whilst [the supply chain contracts] will be locally beneficial, they are relatively small beer to the £18bn value of the project."
Commercial director for Hinkley Point C, Ken Owen, said: "I'm highly positive that Hinkley will be built and my job on the project is to get the supply chain equipped and ready to go."
He said the contracts were for a mixture of services, and 660 jobs would be created locally.
Mr Owen said: "We're not just building a power station, we're servicing a mini-city. We've got 5,500 people per shift, per day. We have to look after the catering, the welfare.
"We're building the largest hotel in the UK - 1,500 beds per night - and the management of that is being done by local businesses."
The total value of contracts for South West firms now stands at £450m.

The Boulogne prosecutor said Gen Christian Piquemal, who is in his 70s,  was suffering from poor health. He was released on bail, according to reports.
Gen Piquemal is accused of helping to organise the rally on Saturday.
Police had told supporters of the anti-Islamic group Pegida to disperse, and then fired tear gas to break them up.
They were taking part in a Europe-wide demonstration against what they say is the Islamisation of the continent.
The northern port city of Calais is home to thousands of asylum seekers who are living in a camp known as the "Jungle" while they try to slip illegally into the UK.
Gen Piquemal was one of several people arrested on Saturday. News of his release on Monday was greeted with cheers by a group of his supporters gathered outside the court in Boulogne. They than sang the French national anthem.
Some reports on French media said Gen Piquemal had been admitted to hospital on Monday morning, but this was not confirmed.
Gen Piquemal, who commanded the elite French Foreign Legion for five years, is accused of playing a "principal role" in organising the illegal demonstration. He could face up to a year in prison and a heavy fine if found guilty.
Gen Piquemal was one of about 150 Pegida supporters who had gathered in Calais chanting slogans such as "We must not let Calais die" and "Calais is part of France".
At the time of his arrest, Gen Piquemal said he was "shocked" that officers had broken up the protest during the singing of the national anthem.
"I expected you to be at attention, singing with us but not one of you opened your mouth," he told them.
French authorities had banned all rallies in Calais "regardless of the organisers".
Contracts worth £250m for the proposed Hinkley C power station have been announced but a campaign group claims the deals are "jumping the gun".
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The court hearing for a former French Foreign Legion commander arrested at a banned anti-Islam rally in Calais has been delayed until 12 May.