I'm a bit late to the party on this one but, for what it's worth, my opinion as somebody who has shot a lot of UK boar is that 75gr V-Max and .243 would be an awful combination for shooting wild boar with and I would have hoped that the guide who has accepted your booking would have told you that! 75gr V-Max will be a recipe for shallow wounding and lost pigs.
I no longer allow anybody to use a .243 on boar, full stop, period. There has been enough debate on here and elsewhere about its suitability for larger deer, let alone wild boar. Let's not re-open that can of worms but take it from me, in the early days when I first started shooting boar and taking mates out, I was relaxed about what guys used and soon learned that .243 is simply not man enough to punch through thick mud caked hair, tough thick hide, shoulder plates, dense bones and then do enough damage to the vitals on anything but the smallest pig. There are guys round here who head shoot them with .243 but I doubt they brag so loudly about their cock ups as they do about their successes!
The Home Office guidance isn't too far wrong at 150gr and .270 although I would be just as happy with 7mm and 140gr. Bullet construction is very important as you are looking for a reasonably tough hunting grade bullet that will punch through a lot of tough material. If the boar of a life time turns up you want to be confident that you have the tools for the job.
The ubiquitous .308 and .30-06 really do take some beating and when matched with 150gr or heavier bullets like Accubonds, Partitions, Pro-Hunters (180gr ideally), Swift Sirocco or equivalent then you have something that will do the business every time so long as you do your bit.