Basing in Newport Pagnell while job-hunting in London

I have some relatives in the UK who live in Newport Pagnell in the midlands (near Milton Keynes). I was wondering if it is viable to base myself in that while I look for jobs in London to save money while being unemployed. Or, is it better to base myself in London during the job hunting process?

How much does it cost to go to London from Newport Pagnell to go for interviews and job-hunt?