I'd like to rent a car in the Replublic of Ireland, tour the Republic and North Ireland and then cross over to Scotland via ferry with the rental car and tour Scotland and Britain; then return to Dublin via ferry and to return the car. Is this plan feasible or even viable? We would be traveling with a party of four.
Will depend on if the rental company is willing to allow ferry crossings and or trips into differing jurisdictions, and if so, whether what kind of fee they want.
Enterprise for example do not permit vehicles hired from within the Republic of Ireland to go to Great Britain without additional permission (although Northern Ireland is fine) and the fee for this used to be €100. Yet vehicles hired from within the UK in Northern Ireland can be freely taken either into the Republic of Ireland or to Great Britain without any additional fee or permission.
AutoEurope will tell you that your damage protection is not in force while on a seagoing ferry. Has anyone tested this claim?
If your car rental firm allows the car to be shuttled, and if any associated fees are acceptable to you, also consider the cost of transporting the car back and forth on the ferry. Ferry fares will be higher for a passenger with a vehicle than for a foot-traffic passenger. Depending on your circumstances, if might be preferable to rent an Irish car, turn it in (or park it at the docks), take the ferry over to Scotland, rent a Scottish car, then return to Ireland where either your first car would be waiting for you, or you'd need to re-rent an Irish car. Depending on how long you were away in Scotland, of course, you might not want to be paying rent on a car sitting in Ireland, awaiting your return. Either way, you'll be used to driving on the left at that point!
Sounds like taking an Irish rental car to Scotland and England would be a hassle. Are there rental agencies where the ferry lands?
We found a bunch of local rental companies throughout Scotland on last summer's trip. In addition to international companies like Hertz, an Internet search will turn up Scottish companies that will often have a desk or office at airports and/or ferry terminals, or can shuttle you to/from the ferry landing. Small companies may not serve everywhere, so you'd have to check based on which ferry you're intending, but there's a good chance you could arrange a rental that would be available when you step off the ferry.