Starting out

Sounds like a great little target you've set yourself - I hadn't been on a bike for 15 years either. I started back in Autumn 2011 and by Feb/March 2012 was on clipless pedals and happily riding with a club.

I'd say don't over-analyse it, when I started I was pretty shaky, but just getting out on the bike regularly deals with that. I also found I lacked stability in turns and descents, but a few core-strengthening exercises sorted that out.

Don't worry about going fast either, the bulk of your riding should just be moderate intensity, so just enjoy yourself.

In terms of skills, do you feel the need for something like a bikeability course?

Don't get too worried about it. We don't say 'It's just like riding a bike' for nothing. If you are feeling nervous start out on a tow path quiet back street or a shared use cycle way. I bet you'll be full of the joys of riding in no time.

When you do ride on the road, give plenty of space when passing parked cars so avoid being hit by an opening door, stay alert to everything that's going on around you and don't ever assume that a driver has seen you or is looking out for you. As long as you recognise that you are totally responsible for your own safety you'll be fine.

Good luck and don't delay getting started.

Yeah good point by Super, several of my first rides were out with a friend who had a a decent amount of road cycling experience!

As above, enjoy!

Do you have any local riders who'd be willing to go out and ride with you to help get your confidence up?

I started at the start of last summer.
Wasn't too worried about safety but I can understand why you would be.
I started off on very quiet country roads and take it a few miles at a time maybe 4-5mile loop around where you live. Best times are very early mornings and and sundays (esp early sunday) barely any cars around at these times. Possibly late evenings (post rush hour) though not ridden out enough at that kind of time. You can build the confidence up and with that the mileage will come.
A rear light and front light would be a good purchase as these will help you stay visible (they are essential in low light in my opinion)
Never cycle too close to parked cars, just in case a door opens in your path.
Pay attention to whats going on around you, you need to be more aware than if you were driving (if you drive?) esp at junctions, roundabouts etc. Take up defensive positions in the road when appropriate. Read the road and plan your moves.
A helmet (braces for helmet argument) A neurosurgeon told me that the amount of cycling accidents he sees involving head injuries can often be prevented through the use of a helmet (don't trust him though...I mean he's only a professional) Helmet is personal preference I know but I think its advisable.

If I think of anything else I'll add.

Most of all, don't worry too much about your safety and have fun. Most drivers are courteous and understanding, will give you appropriate room and are patient. If someone confronts you about being a cyclist(I usually ask if they'd like to pull over and ring the police, this shuts them up pretty quick) just keep calm and try explain your side.

Again HAVE FUN