Put these factors in order ....

Seems I pass for crew and helm then ...

It is slightly confusing to agree with someone and then find them telling you why you are mistaken. I thought we were both arguing that boatspeed differences are less significant than other factors, at least in our own classes. I wasn't discussing boat-handling.

But in terms of boat-handling, S/38s are heavy and relatively underpowered boats that most certainly don't accelerate quickly from bad tacks, and any kind of keelboat will bite you hard for boat handling errors downwind, especially in a decent breeze.

Do you have to concentrate on moving your feet when you walk? Helming should be as natural as walking. If it isn't, you need to spend more time at the tiller. You can bet Ben Ainslie isn't "concentrating on driving". He is thinking tactics, wind-shifts, current, other boats and boat-tune. 

That said, one of the best things I found about being the driver but not the skipper on other people's big boats is that I could just concentrate on making the boat go fast. All the other stuff involved in running a boat with 9 people on board was someone else's problem, whereas on my own boat I had to deal with it as well as steer. Nevertheless, "making the boat go fast" means talking to the trimmers all the time to get the boat going, not just waggling the wheel and staring at the tell-tales.

Im well aware I need to spend more time on the tiller, spending less time in borrowed boats would also be great cos I could spend less time trying to remember if the blue string is in/out or up/down on the jib cars and which color the kicker is on this boat 

As you said above being the driver but not the skipper on a big boat is easier than running the whole crew. When Ive got main in one hand, tiller in the other, one eye on the tell tales, one eye on whats around me, one ear listening to my crew, part of my brain thinking about how the boat feels and part of my brain thinking about what I want to do next its no wonder that working out what bit of string might help, finding a spare eye to spot it and a spare hand to ajust it can sometimes slow me down a bit......

As for trying to walk under cars, there is no traffic were I live!! And I'll probably be even worse after a few more months in USAland, even if I remeber to look, Ill look the wrong way

We are talking at cross purposes. The original point I was responding to was crew saying "Shut up and steer". My argument is that it is the helm who is in the position to call overall boat tune. Crew just doesn't have the same feedback the tiller provides (and I've done plenty of crewing as well as helming). Who pulls which string is another level of detail. The helm shouldn't be doing things the crew can do and the boat should be set up so the crew can do as much as possible upwind.

If the helm is bobbing about trying to pull strings then either the boat is laid out wrong or the helm just needs to learn to do more than one thing at a time. The helm ought to know exactly where controls are without having to look for them. Nobody said it is easy.

I once talked to the guy who has won more Salcombe Merlin Weeks than anyone else in the last 15+ years. Sailing at Salcombe often involves long short-tacking sessions to keep out of foul tide, every 20 seconds or so for upwards of a mile. Before every tack, he eases kicker, tightens main sheet, roll-tacks the boat, eases mainsheet while head to wind, pumps the main back on as the boat is rolled upright, centres the traveller and pulls kicker back on  as the boat accelerates. All of that every 20 seconds for 15 minutes or so. I get exhausted just thinking about it.