Reneging on a Training Contract offer

Guess you have to check the terms and condititions and see if there's a financial penalty. If you've signed then it is legally binding if there's a clause that talks about recouping financial costs. Likely they'll be sympathetic before you actually start. I'm gonna be honest and say I have never been bound by such a contract so it's difficult to say. Pulling out shouldn't affect your future applications, happens all the time.

nothing bad will happen unless the firm has spent money on you e.g. by funding your GDL or LPC. you'd be expected to pay that money back.

reneging is common.

keep in mind that the TC will require you to end all other applications to other firms. most ppl who renege don't do this and assume that sort of clause cannot be enforced in the real world. i think that this is a fair bet as HR don't talk to each other and have no reason to share a list of candidates who reneged with each other.

However, the TC offer actually has no mention of a requirement to end all other applications to other firms, so I suppose it's only the voluntary guidelines that have any bearing and they are 'only' guidelines...