If he is not in arrears, the lender can't do anything.
But if he is not in arrears, why was the loan sold? UB says that only loans in the court process were sold.
They could increase the interest rate but are unlikely to do so.
It's likely that they got a good discount, so they might be open to a deal, i.e. giving him a discount if he refinances the loan elsewhere. So he should organise his affairs to avail of any such offer. In other words, only invest in liquid assets in case he needs to sell them.
Brendan