Horizons Unlimited - The HUBB - Advice Requested on RTW Visas and Borders Crossing with UK Passport

Hi,

I'm hoping I might be able to ask for some kind help to validate and clarify my visa plans for a RTW trip this year.

I've been away from HUBB too long, mostly to stop torturing myself over trips I want to do but couldn't afford or get the time to do. However, all of a sudden it looks like I might be able to be made redundant and fund a RTW trip, so over the last few weeks I've been reading up again and putting together as much info as I can find. I now think I've got a good base of knowledge, but would really appreciate some advice.

Below is a table I've put together of visa & carnet needs for a UK passport, but I'm aware that some info may be missing or out of date.

Would be great if anyone could add or correct info on;

Visas - if needed (in advance or border) and the cost, best place to get and requirements or limitations (i.e. transit only, starts from time of issue) - Particular ones that are making me nervous are Nigeria and DRC.
Suggested border crossing (and ones to avoid) - I'm really lacking in this regard
Carnet - any insight on the 'Recommended' list would be great - Are all of these likely to use carnet or is it just a case that they might ask - i.e.Don't want to get to extorted at every police block if I haven't got it stamped when it was 'recommended'

Finally, less important but equally appreciated would be any info anyone wants to volunteer on;

any areas on the route where I might have fuel issues (i.e. longer than 250 miles without petrol or where there may only be leaded)
Any insurance or road tax needs - particularly at borders
Any accommodation where it's good to meet overlanders / bikers
Any info on the ability / legality to wild camp

Almost forgot to say, I'll be travelling on a British passport

Thanks

James