Hi Richard
I don't have a huge amount of experience with "big pigs", but I'm pretty sure that if you get a couple of weaners now, then they would be ready by Christmas (so avoiding keeping them through most of the bad weather).
Looks like you've done most of the groundwork - attending a pig keeping course etc & have ready made housing & a decent area to keep them in

To be honest, raising a couple of weaners is a good start - it's when you get down to breeding the more intricate stuff starts
You'll need to register with eaml for movements etc & contact your local AH for your Herd Number once you've got your weaners, scource a reliable (& hopefully cheap) feed supplier & ensure you have a way of ensuring they have a constant water supply. If the breeder has (& should really) wormed them, then you shouldn't need to deal with any meds. Make sure you will have suitable transport to take them to the abattoir when the time comes - what you need to do about booking them in, tagging etc. Oh, & that you have access to a vet that treats pigs, as many of them don't, just in case
I would advise going to a breeder rather than a Mart for you first purchases - as you can see the welfare condition of the sow etc & you have a contact for aftercare advice & support.
As for the breed - everyone has there own "favourites" - if you can afford to buy from a registered rare breed it'll support the continuation of the scarce lines, but if not there are some great cross-breed that make marvellous sausage & bacon.
Sorry, I've been good so far ... but, I've got to put a word in for the wee guys

... I would recommend consideration of Kunekunes for a 1st timer - very docile & easy to handle, hardy, very cheap to feed (compared to most breeds), don't cause as much damage to the ground as "big pigs" - by scale of size (don't ever believe that they don't dig) BUT they probably wouldn't reach meat weight by Christmas if you get weaners.
Whatever you go for - let us know how you get on