(thanks for response ewa.swimmer, but it's not a race, more of a charity swim)
Here we go then Westy, my input…
all fairly obvious, but I think it's a combination of little's that make the difference, rather than a single solution!
just as Terry Laughlin explains how small muscles tire easily, then my figuring is they probably don't have the capacity to generate (a lot of) warmth. So I've started over-extending, over-rotating, over-'anything' really, as long as I'm using my core! My stroke rate has probably dropped slightly, rather than increased, but I'm putting a lot more effort into each stroke.
Even thou my wetsuit looks as if it's painted on I've managed to layer a 0.5mm neoprene, titanium lined, (Thermabase?), short john, underneath.
I had a swim cap, which luckily disintegrated, and while searching for a new one I came across a pretty thick neoprene 'helmet', with a chin strap. I layer this with a neoprene beanie - helmet underneath. The helmet also keeps water out of ear-plugs/ears. Those large goggles Terry Laughlin wears in his DVD's are great - sounds mad, but they tend to keep your face warmer than the small 'swimming pool' type goggles.
Try and train later in the day if it all possible, and make sure you eat (& drink) enough - I was training 1st thing every morning on nothing more than a fruit juice. Acid reflux tends to affect me, in the pool (if I'm careless with eating practices), more so than in very cold water, so I make sure to pile in the calories.
If cramp's affecting anyone my solution is to curl up into a foetal position for 20secs (wetsuit keeps me afloat) every lap - my laps working out at 1/2 mile intervals.
If chafing's a problem there's an amazing product (called Lanacane in the UK), that resolves the issue.
Suppose I've just 'advertised' a product there - am I allowed to do that? If not apologies, if I am I should've also mentioned companies responsible for the thermal short john, and the helmet.
And finally: urinating in your wetsuit! Not sure if it's the actual act of urinating, or the fact you've just 'injected' a warm fluid into your wetsuit? Sounds awful, but definitely works.