Taff Trail, South Wales
This is a 55-mile largely traffic-free route from the center of Cardiff up to Brecon, passing Pontypridd and Merthyr Tydfil on the way. You don’t need to cycle both ways because the Brecon Bike Bus connects Cardiff and Brecon on Sundays between May and August. Sustrans’ Lon Las Cymru South map covers the Taff Trail and more.
Bealach Na Ba Circuit, North West Scotland
Explore the Applecross Penninsula, which is simply across the ocean from Skye. Cycle clockwise from Shieldaig, taking in Britain’s most spectacular road and only alpine style climb – that you’ll need very low gears. The 43-mile circuit might be wiped out each day by fit families with tandems or teenagers, otherwise you could camp or B&B in Applecross.
The South Downs Way, Southern England
A 100-mile off-road chalk hills trail between Winchester and Beachy Head. It’s not technically demanding in mountain biking terms but it does require an honest level of fitness to try to to the entire thing. Allow three or four days, or simply do bits of it.
Land’s End to John o’ Groats
Ok this is not for beginners, but it gives you something to aim for and you’ll roll in the hay in small sections because it is Britain’s ultimate big ride. Most of the people take three weeks to cycle a scenic 1,000-mile route from the tip of Cornwall to the highest of Scotland, covering around 50 miles each day. Children as young as nine have ridden this on their own bikes, but it’ll be easier with tandems, or older children. Cycling UK have an End to finish information pack, which is out there liberal to members and there’s a superb Land’s End to John o’Groats section on the Cycling UK Forum, it’s full of advice from many cyclists who have cycled the top to finish and may be a excellent spot to ask questions.