Hi Jimbo
If you're reasonably fit and don't mind a few climbs, the coast road from Padstow to Newquay is without doubt one of the most beautiful roads in the UK and an absolute peach to cycle. You will end up going either up or down for most of it, but the descents are worth it, some of them are a bit nasty at the bottom though, especially the one at Watergate bay.
Take a break at the National Trust Cafe at the top of Bedruthan steps, great nosh (at a price).
Just do it, you'll not regret it.