Sorry about that, missed it on the summary. I'll add it in. Foul gets +£60 that turn, UP gets +£6. Caravans are destroyed upon use; you need to take into account the £1000 you spend building one when calculating the profits of its journey. Since caravans even with that restriction tend to make a much higher profit than ordinary buildings, that isn't too bad provided you are at least 4 territories/1 territory + an ocean region away from your target. Remember that the more you use caravans, the more likely neutral territories will start sending out raiders to intercept them.
Materials won't give bonuses to units, they'll just make units available or cheaper to build. This is indeed partly because I code most of this in, although it would be relatively trivial to give bonuses to that effect (I'd just manually add in a faction bonus of the right amount, as I am currently doing with wall bonuses because the territory/building scripts aren't even written yet). The other reason for this is that because iron and copper are both needed to make certain unit types at all, just having access to said resource and getting a bonus would be redundant. Assume that if a material type is not needed, the requirement for that resource is small enough that most countries can supply it with the trace amounts of the material found in their own territory.
However, as a note on researching units; Higher tech-tier units will generally be at least slightly more efficient than their unresearched cousins. Material-dependent units will generally be more powerful than their non-dependent brethren. I will not make units have a special bonus if they have access to a material (as JF wanted for Auxila/Skirmishers), because while I could probably code that it would not be worth the time invested and lead to more unnecessary donkey-work on my part.
The Dark Whisper spell acts like an infantry unit; it can travel a certain number of territories per turn and will continue travelling until it is exhausted. I was considering having it have a move of 2 but be affected by roads (halved movement points), but now I am considering just giving it a move of 3. Hmm. Yes, Dark Whispers have a move of 3 (I'll update the post). now has the 'Ranged Spell' special and can be used on any target it has a clear path to within 3 territories of the casting wizard. You can summon as many DWs in a turn as you can afford, though each one of them will be destroyed in an attack or in defense (like Dark Wards). So yes, that does mean that you could just spend £1200 and spam a 4-man defended territory with DWs and have a very good chance of ruining their defence. But Dark Whispers can't conquer territory, so you'd better send troops in afterwards. I'll add that to the post.
Presently this makes Dark Whispers powerful, perhaps too powerful. I will consider nerfing them if I have to (or maybe rebalancing their counter-values so there is practically no chance of them winning a defensive bout), but mostly I am taking into account that it will be possible to research units and defences that provide bonuses against spells and spell types (such as curses) that can be large enough to negate this sort of effect.
Edit: Remember that you cannot cast Dark Whisper or Dark Ward unless a Necromancer unit is present in the same territory when casting. This counts for all spells. If your caster is killed or wounded, you cannot cast.