After a little more digging i think i will go for a PLB.I am getting a price for the fastfind 210 and the new fastfind ranger. As vipa says it will have to be a satelite based unit.The fastfind unit has no subscription and the battery lasts five years,a one use unit, but as long as you can activate it you will be found.not to be used for a sprained ankle i think,but pease of mind counts for a lot nowadays.
Cheerglen