what ever time you have spent with one insurer will transfer with you. if you have passed your 5 years for the pre-existing conditions with vhi, then your 5 years is up.... if the plan with vivas is a higher level plan, then may be extra waiting periods.. e.g. if you change from a plan that covers only public hospitals to private hospitals you would have an extra waiting period.....
as afar as residency in ireland, you have to be resident in ireland 6 months of the year...
about the treatment abroad ? are you going specificaly abroad for treatment ?? is it not available here in ireland ?