Was also going to suggest Cairnryan - Belfast or Larne, which is a fair bit cheaper than the ROI crossings. Plus there is a nice C&CC site nearby (the only one on the island) at Delamont handy for the Mourne mountains, Downpatrick and Belfast. Even the Giants Causeway is driveable in a day. If you are National Trust members there are 2 excellent houses nearby at Mount Stewart and Castle Ward.
Camac Valley might also be a good place for you to stay, handy for both Dublin and the Wicklow mountains and gardens. Kilkenny and/or Tipperary are good places particularly for history. Then of course theres the more normal Western tourist areas of Cork, Kerry and Galway.
Don't forget to leave a review of the French and other European campsites you have visited!
If you are going to be doing a lot of sightseeing, the OPW (similar to National trust) do free Wednesdays or you can get the card for Euro 40 which seems expensive but you will make it up in about 3 visits.
------------- Hypercamp Alaska
Vango Force 10 mk3
Vango F10 Helium 1
Coleman Cobra Pro 3
Coleman Cobra 2
Naturehike Star River 2
Eureka! Solitaire
Dutch army goretex bivvy bag
I'd want to go back to the place my grandparents came from. Folk with family connections don't come to Scotland and stop at Glasgow or Edinburgh, they seek out the crofting settlement on Skye or the tenement house in Greenock or the estate cottage in Perthshire. If OP goes back to his roots, oh what a welcome at the pub, someone might know of the grandparents or why people left when they did (potato famine, possibly), look in the graveyard for others with that surname, there may be a local museum....
Ireland north & south has fabulous places & people, but with 8 days, you can't see it all.