A belated response to you, Pete:
1) You do not need a cold storm or a winter passage to feel cold on a small boat at sea at night. If the water temperature is 60 degrees F (15 degrees C), you are going to feel cold at night even in good weather; if you are wearing cotton clothing, your teeth are going to be chattering.
2) Note that, while the IF is not a sportboat, it's not a total dog in light air. My nylon drifter headsail is a 155% nylon genoa that hanks onto the forestay. It can well make a difference between doing 1 knot and doing 3 knots. I'd be interested to hear if someone has a better idea for light air sails on an IF. The IF in the slip next to mine was rerigged with a masthead genoa and a forestaysail. The mast had been upgraded to a larger-diameter two-speader mast. I don't know if all that was worthwhile. It was bought by a fellow who sold his standard IF to buy it, so obviously he thought it was worthwhile. He recently sailed it from San Francisco up to Humboldt - normally a notoriously rough passage where many vessels have been lost - and arrived safely.
3) The patch (actually, Transderm Scopalamine) is a prescription drug in the US, but I suspect may be over-the-counter in the UK. The instructions say to put it on 4 hours before going out, but in my experience it works faster than that. It will repress seasickness without making you drowsy. It may make your mouth dry or slightly blurr your vision (I have not noticed a vision problem at sea, but I have when driving home from the marina). Being able to go below without feeling sick makes a big difference! Also, a trick that a wise old sailor taught me is always to sleep on the boat the night before going out.
4) My jacklines run from the forward mooring cleat back to pad-eyes that I have put in on deck on each side of the boat about 6 feet (that's about 1.9 metres) from the stern. My tether is about 6 feet long; the idea is that I can't be dragged behind the boat if I do fall off. My jacklines are webbing that I bought at the local marine store; many folks go to mountain climbing stores and buy their webbing there. There's a vast literature and discussion on sailing blogs about jacklines and tethers. Some folks say that lifelines are useless and even dangerous because you can trip over them and fall overboard. Personally, I wouldn't be without them. When I go on deck, I crawl if it isn't dead calm; I find the lifelines very helpful. The interesting question is, when you fall off and are hanging by your tether, how do you get back on the boat? I carry a mountain climber's ladder in the pocket of my foulies, with a hook at one end that can go around a stanchion. A buddy of mine actually jumped overboard in full foulies and was able to get back aboard this way -- at the dock! Only King Neptune knows whether this would work at sea. So remember, one hand for the ship and one hand for yourself -- don't fall off in the first place!
5) I don't think you need two outboards. Your question about rowing is an interesting one. I think you could row an IF in calm water, especially with a proper oar and rowlock, and perhaps with some practice. I carry an oar, but I don't have a proper rowlock. I once tried to row, without success, but there was a chop running. I have meant to try on a calm day on the estuary, but I haven't got around to it. I have heard that, to do it right, you would need a rowlock mounted on a pole about 18 inches (.5 metre) above the deck and an oar about 12 feet (3.5 metres) long. Perhaps you should post a separate thread about rowing an IF; people may have some suggestions.
6) Regarding fog, a masthead strobe light is illegal inshore and might be taken as a distress signal offshore, but will enhance the chances that you will be seen. Some folks have radar, but there are drawbacks on a boat as small as the IF, not the least of which are how much space it takes and electricity it uses. I don't know if they require ships in UK and European waters to carry AIS transponders; lots of small boat sailors here are talking about getting AIS receivers, which use little electricity and make it easy to avoid ships (but are useless in avoiding fishing boats, etc.) You should have a depth sounder; if you are in 5 fathoms, you can be sure you will not be hit by a supertanker. I also strongly suggest a GPS chartplotter so you can see at a glance whether you are in the shipping lanes. As I said before, I've found monitoring vessel traffic stations on the radio easy and very effective.
7) I have an anchor bracket on my bow pulpit, but I have found that putting the anchor there blocks the running lights and means the chain is far forward on deck, which is not the best place for it. Also, twice the anchor popped out of its bracket while underway! I don't know about a roller bracket.

If I were going out for more than a daysail inshore, I'd carry a porta-potty (chemical toilet). In the US, a standard marine head is illegal inshore unless the boat has a holding tank - I bet the requirements are the same or more stringent in the UK and Europe. There's not much room for a holding tank on an IF; I don't think it's worth the effort to put one in; it would be interesting to hear from someone who has put one in.
9) I have never had green water over the cockpit coamings of my IF, and I suspect few IFers have. I think there was a post on this board a few years ago saying that the cockpit scuppers are not as large as they might be, and that it's not practicable to enlarge them.
10) I have a single board with a vent to close the companionway, and I also have a plexiglass board without a vent that I've never used. I think a single board is superior to slats.
That's long enough for now, Pete! Good sailing, and let us know how you make out. Regards, Tom Kirschbaum IF 637 Feral