Try Scilly (never "the Scillies" or the "Scilly Isles," by the way). They're lovely. All very low and gushing with wild flowers in spring. Tresco is the most commercialised but it's easy enough to stay on any of the others and island-hop on cheap boats, which abound. The Abbey Gardens on Tresco are a must. St Mary's is the biggest island (though you can walk right round it on a relaxing day) and has the most accommodation, but my favourite is St Agnes. You simply can't beat a ramble round St Agnes and Gugh on a sunny late-spring day. If you like camping there's a fabulous campsite there and an even more fabulous ice cream shop attached. It's a bit expensive is Scilly, admittedly. I imagine that he Channel Islands are too.