Getting back to Poole Harbour, flying boats weren't the only aviation there. The Royal Motor Yacht Club storage centre at Sandbanks was obviously a hangar for smaller aircraft during the war. Painted storage spots for various Kingfisher & Gosling rig boards & large tools were still to be seen on the back wall in the 70s.
IIRC British Powerboats also operated out of Poole - think they also built tenders for the flying boats as well as MTBs & Air Sea Rescue launches there.