Hi and welcome!
Sadly, far too many breeders and shops still sell baby boar trios without acknowledging the fact that up 90% of them need separation during the hormonal teenage months between 4-14 months of age until they reach a more settled adulthood. 6 months of age is a typical spike time.
Please be aware that if you neuter, you will need to research for a good general vet with lots of practice in piggy neutering (often for a rescue) or a small animal specialist in order to minimise especially the otherwise much higher risk of post op complications.
You also have to factor in a full 6 weeks post op wait until a boar is 100% safe to go with a sow. I have the surprise baby courtesy of a supposedly safe over 5 weeks post op rescue boar living with me, just to prove that particular point!
That said, cross gender bondings are the most stable once initial acceptance has happened. if you want to go cross gender, please keep the mixed pair on the lower level, safely out of sight and reach of pheromones from the boys. Unfortunately, your little boy is facing some time on his own for the sake of a happy future. We have got bonding advice as well as experience on here. You are also welcome to start a thread for ongoing support and tips before, during and after the op in our health/illness section. You will have to keep him indoors for the initial recovery period.
It would be good if you considered bringing your piggies under cover for the winter; we are getting our first frosty nights this week.
We have got a piggy savvy UK vets locator on the top bar, as well as a recommended good standard guinea pig rescues locator. Sadly, Essex is a bit of a breeder county, so we cannot list any rescues from there with good conscience and have to send you out of the county for a good rescue we can guarantee for. There is one in Chelmsford that runs to a good standard with quarantine and pregnancy watch if you don't mind that they take in unwanted breeder piggies (and are indirectly supporting breeding and - sadly to say - breeder's attitudes as the one you have encountered) and not necessarily rescues in the strict sense.