Any legal experts about?

[temporarilycross]

I accepted a job and signed a contract, stupidly as I felt unsure about it. Nevertheless I did and the job begins on 30/8. Today I've been out of the blue offered my ideal job in a place very close to my home. I desperately want it but realise I could get into trouble.
What are the legal implications if I didn't start the original job?

They can't hold you to anything as you have not started yet. Even if you had, you can give notice, so tell them now [with 8 days notice] and let them offer it to the next person.

When you say you've been offered another job, to what extent is that new job signed sealed and delivered the a contract of employment and they're now Itching to get you onboarded in a week's time?

I wouldn't give up the currently job unless everything is in the bag and you know there's no chance of the new company pulling the rug out from beneath you by not giving you the job after all.

You've signed a contract so you can be held to it, whether you've started work or not. You have signed a contract agreeing to start work on 30 August. If you want to get out of the contract you'll need to give notice. How long is the notice period?

What you'll probably find is that if you give them notice now they won't want you to bother starting work even if you haven't given enough notice to terminate.