Ok to turn down job after accepting?

As you've signed a contract of employment and are not honouring the notice term that will be in there, then there are potential legal implications if you do not show up for work. They could ask you to re-imburse any advertising costs and any administrative costs associated with processing your application, and pursue an action against you if you didnt negotiate a settlement. Having said that I would be surprised if they do - but they could. I would write a letter explaining the reason for your decision - don’t expect a job with them in the future! Just a final point - you don’t want to be in the position of not having any job, so I wouldn’t do anything until you have a firm offer of employment in writing from the nearer employer. Hope everything works out.

Much better to turn it down as soon as possible, but do the decent thing and explain why - not least because you may need them in the future.

The commuting time is a reason most people will understand, especially if you have a young family. I wouldn't mention the salary issue, because if you, they may offer you more cash and then be really annoyed if you still say no.

Legal issues? Shouldn't be any - it would be nigh on impossible for them to show they have suffered actual financial loss directly attributable to a first jobber not showing up!

Personally I wouldn't be very happy and would be very unlikely to offer you a job in the future if you needed one. However in business you get used to being disappointed by the workforce.

The only thing I would tell them would be the travel issue, don't mention the higher salary. I haven't seen the contract you signed so I would ask them politely if there are any legal implications if you chose to work for someone else for family reasons.