.... and have very much enjoyed rallying around my local country lanes today ...
Only a "young lad" would write this and then lament about how someone pulled out in front of them. Imagine if it was some kid on a horse, rather than a Fiesta. Unpredicatble stuff happens. Just slow down a bit and everyone will live longer.
But "..30 yards..." you woulda made it, don't worry..
Car would be doing about 20mph by the time of an impact.
If you're going to hit something, aim for the space between the rear wheel and the B-pillar. Not either wheel or the drivers door ... since the former will damage your car more and the latter will probably injure the other driver quite badly .. though arguably they might need that wake-up!
It's better to be pointing towards the kerb too, so you don't get deflected across the road. A head-on with another car will be pretty severe and would also just complicate the insurance forms..
On the other hand, don't drive into a ditch to avoid an accident since there will likely be a tree there which will be pretty nasty for whoever is in the death (aka "front passenger") seat. If you have an accident trying to avoid one, you'll find that the other fellow has driven off and you're paying for the damage... it's arguably better to bend some metal...
Whether you can make all these snap decisions in the middle of an accident depends on how quick you can work through all the options. Sounds like your instincts are pretty sharp.. but give yourself more of a chance next time. Less "rallying" .. more "driving" maybe..