There's a place called The Halwyn near Manaccan, which is near the village of St Keverne. It's a converted farm, with 6 units to let, depending on numbers or budgets. These units include the old farmhouse (sleeps 12), the Halvilla (6-8), the Granary (4-6), the Hayloft (4-6) and a couple of other small units (2-4). Each of these offer normal mod-cons and would be fine for the average family but don't expect decadent luxury! Don't come here if you're looking for an Olympic-style swimming pool or one suitable for diving, but if you just want a safe, warm, clean pool adequate for a couple of short, lazy lengths, it's just the thing.
I've been to this place with my family for about 20 years on and off and I love it as I've grown up with it. Go to www.thisiscornwall.co.uk and look for links to holiday accommodation.