Don't forget to print off your paper counterpart code from DVLA, as many hire companies will need this code.
Those are no longer valid. I thought you needed a code from the DVLA website? (Which lasts for three days) I've heard of them asking for National Insurance numbers, PLEASE DO NOT give them that, they don't need it. Although isn't ROI covered by your normal UK License anyway?
Personally, I'd ask the rental company and get it prepared before. The damage waver is up to you, ask what the excess is, but also consider a supermarket dink will be your fault, again I've always took it and never needed it.
EDIT
Opps TB has covered that, I misread it
To generate the code (valid for 3 weeks IIRC) you need driving licence number and NI number.
The hire company need licence number and code.
Its possible this is where some confusion arises, or that maybe people of turned up without it, and the hire company have helpfully produced the code there and then.
There are 2 ways to do this, both involve going online to DVLA website. You can either generate a One Time Code which is only valid for 72hrs but doesn't require you to print anything. Just make a note of this code and give it to the hire person when you collect the car. Alternatively you can print off a Licence Summary which is valid for 30 days, however you must print this and hand it over at the time of your hire.
So far our team at work has managed to hire cars in France, Spain, Germany and the USA without being asked for either of the above. Seems like the message hasn't filtered through yet about the changes.
The hire companies can generate the code for you on the spot but I suspect they don't like doing it as it takes time & effort. They will also probably start charging an admin fee in the future!