It's a SCAM>
UK companies cannot hire people from outside the UK/EU without interviewing them. It's not allowed under UK immigration rules and they have offered you a job but you have never contacted them.
Unless you are capable of managing contruction projects in excess of GBP 300 million, and are being rexcruited as a project director, you are unlikely to be offered a salary as high as this.
They will ask you to contact an agency to process work visas. It's not done that way, the UK company deals directly with the Home Office, no middlemen involved. They will ask you to contribute money to processing the documents. If offer was real, sponsor company would pay all costs
They will ask you to send money by Western Union. Real company would not ask you to use this method of transferring money. It's untraceable.
They ask you to provide them with personal information (passport details, address, bank details etc).
Do not respond to them - you will be put on a 'mugs list' and your details sold to other criminals.
Do not send them money - You will be helping to fund criminals and possibly terrorists.
Do not send money via Western Union to anyone you don't know personally.
Do not give them any personal details - beware of identity theft or bank fraud. Your identity may also be used to commit further crimes against other innocent people and this could cause you serious problems in the future.
If you have given them any details, please read this.
Please let as many people as you can know about this scam by emailing your address book and asking them to also pass it on. Knowledge is the only way to stop these criminals