What percentage to cover devaluation?

I was thinking of moving a percentage of my money to a Sterling account in the North,

To try give myself more options in the event of Ireland leaving the Euro.

I’m looking at break even situation and was wondering has any economist put a percentage on what we might devalue any new currency by?

I feel even if Sterling went pear shaped against any new currency or even the Euro at least I could just drive to the North and make purchases and the currency switch wouldn’t have as negative effect.

Nobody knows, how much New Irish Punts would devalue by, if the EUR breaks apart, but most people accept that it would devalue significantly.

I have read some articles that said it could be 20% while another article said it could be over 40%. All speculation.