Statutory Redundancy Repayment

I'm about to be made redundant from a big organisation, and there's an opportunity to apply for a job with the same business in a different area on less money (...I can always work my way back up).
It's not a "suitable alternative" so won't affect my redundancy payment from the company, but does anyone know how long I have to be away from the company for it not to affect the Statutory Redundancy Payment?
Thanks