I was interested in your report of a sailing area I know well (as a former YM Instructor from Cowes). I'm glad to hear you're all OK, however there are a couple of points that you should be aware of:
1. "At the Needles channel, the wind picked up to 22 knots to 28 from the SW, directly against the strengthing ebb tide"
~ Apparent windspeed is increased significantly by a strong 'weather-going' tide.
2. "We decided it would be dangerous to run with the wind up the North End, in shore, because it would put us against a lee shore and we could have had a disastrous jibe with just the main up (which we had).
~ With your reported wind direction of SW, then exiting Hurst Narrows by the North Channel would put you reaching on port tack, with the Shingle Bank to windward of you, before hardening up to close hauled on port tack at the North Head buoy. Thus no gybe needed! Also the Shingle Bank provides an excellent 'breakwater' and smooth water for you to sail fast with minimal leeway. Tacking onto starboard once abeam Mudeford/Christchurch allows you to clear Hengistbury (spelling?)Head and its offlying ledge.
3. "We burned along at 6.2 to 7.8 knots all the way to the Poole channel entrance, where the breaking swells were worse than ever, AND we had to drop the main because it was impossible to run downwind with the boom out (the boat insisted on heading up, over powering the rudder to the point that I thought the tiller would snap from the weather helm)."
~ Entering Poole Harbour downwind against a strong ebb tide is ill advised (in my opinion). Better would be to anchor in Studland Bay under the lee of Old Harry and wait for the tide to turn or slacken. Alternatively, the North Channel is well protected from the wind over tide maelstrom albeit with a draught restriction at low tide. Approaching Poole Entrance from the north puts the wind on the port beam thus allowing you to get inside the entrance before dropping the main in the quiet and smooth of the South Deep.
Just my opinion........
"Seercha" Ericson 26, K'port ME