Yes, it is a classic scam.

No work agency any agency should request payment for a job they offer, especially via western union.
I'm afraid you will never see the money again and what is worse, they may ask you to pay for extra charges. they will try to get as much money from you as possible. They also have your private details and may attempt to steel your identity.

070 numbers are used by fraudsters all the time, this is not a UK number, it is a redirecting number allowing them to use it anywhere in the world.

Please inform your local police of the fact that you have been scammed.