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.
Contracts worth £250m for the proposed Hinkley C power station have been announced but a campaign group claims the deals are "jumping the gun".