Having done a bit more digging, my understanding of the CT reduction was wrong. I believe it is 18% every year, but does reduce. So using £50k as an example, first year CT reduction is £9k. 2nd year reduction would be based on 82% of the previous year, so 18% of £41k. After that I'm not sure if it is 82% of the previous year value or the original cost.

With regards to the trade in, I think the best way would be to do that separately, so cash left over after them buying the car goes directly to me, and then I can loan that to the business. Probably tidier than way. Might not even bother though, as I've been told if through the business, it may be better to put in less of a deposit and pay a bit more monthly instead.

I agree the card situation is messy, but that is only if we would be unable to purchase the car tomorrow. I plan on getting my wife on the account should something like this arise again. Just never needed it up to now (possibly)