Peter, I can not make comment on Ireland, be it Eire or Northern Ireland. However, I can suggest that you consider the North Yorkshire Moors, The Yorkshire Dales, The Lake District and the Scottish Highlands. All offering outstanding scenery, wild landscape, minor roads and tracks, and possibilities for wild camping.
If you are a real punishment seeker, then I recommend that you definately do this Scottish Route. Basically it consists of riding through the Heart of the Scottish highlands. Starting from Stirling in Central Scotland, heading north east to Crianlarich, then up to Fort William (you could here take a diversion and visit Loch Ness the home of Nessie
The Loch Ness Monster.)then to the Isle of Skye, crossing the Skye Bridge, then cycling up across Skye, through the Cullin Mountain Range to the Port of Uig. Catching a ferry (2 hours) across the sea to the Island of North Uist in the Outer Hebrides, cycling down through North Uist and South Uist, to the Port of Loch Boisdale, catching another (this time overnight - 8 hour crossing) ferry to Oban in Western Scotland then heading back to Stirling.
An absolutely fabulous, stunning, exhilarating and demanding ride/tour. It's not that far really, approximately 700 - 800 kms, but is well worth the added effort and time. This was one of the first tours I did. I took my time with it and made it last three weeks. I cannot recommend this enough. I fell in love with every heartbreaking hill, every view and every mile of the journey. Absolutely fantastic and stunning. (Ooops, getting carried away with the praise for this route.)
It's a shame you are coming over this year, if it was last year I would have honoured and proudly guided you round this particular tour. Unfortunately this year (in 34 days) I set off on my own long distance tour heading towards Turkey and beyond.
Please, if anything else, just check out this route, give it some consideration, and research all the places along the route, I really really do recommend it 1000%