Thanks very much for your suggestion. I've discounted the Finn because the boom is too low and a Solo as its got a large impediment in the cockpit.
So far my favourite is a Firefly. Deep cockpit, can be sailed singlehanded (aft main).
What single handed dingy would the forum recommend for a fit 230Lbs (105kg) helm with dodgy knees. Ideally I'm looking for a dinghy with a deep cockpit as I cant fully 'bend the knee' Presently I sail a Streaker but I'm too heavy for it.