There is no difference between the PSV licence and the PCV licence apart from the name and you will find people and companies switching between the terminology which can sometimes be quite confusing but don’t worry.
The PSV licence was technically abolished in 1992 and was replaced with the PCV licence but there absolutely no difference between to two licenses. If you passed your test before 1992 then you will hold a perfectly valid PSV licence and the training is completely the same as those who have the PCV licence. You can drive the same vehicles and so if you see a job for PSV drivers or PCV drivers then you can still apply for them. This is much the same for HGV drivers who are now technically termed as LGV but are still called mostly by their old name.
So the crux of this is … don’t worry as they’re both the same thing.