We did Cornwall in 2010. Joined the Caravan and Motorhome Club just to avail of the campsites
along the planned itinerary. Pitches were not cheap but the facilities were exceptional. We had bikes which were fantastic to get to see the sights. Cornwall is beautiful. Think Kerry except with a lot more rolling hills. Yes the rural roads are narrow, but surely no worse than along our WAW. Loads of tourists, even in relatively low season. Very popular with retirees.
We visited Boscastle (2004 flood), Tintagel Castle, Port Isaac(Doc Martin), Padstow (yes had the fish'n'chips at Rick Stein's), St Ives, St Michael's Mount. It would have been extremely difficult to get into most of these places/find parking
with a motorhome, but easy if you have bikes. We will go back as there is so much more to see.