If I sign a job offer (IT services) for full time role but then decide before I walk in the door with my new employer / I don't want the job anylonger, is that ok, no legal recourse?

Technically speaking, if you signed an employment contract that requires you to provide the employer with notice of your resignation, the employer may have legal recourse against you to enforce the notice period. Practically speaking, you will want to reach out to your new employer as soon as possible to let them know that you no longer wish to fulfil the role in order to provide them with as much notice as possible to replace you.