But because we've been saving for his uni years, we could afford for him to take a smaller loan - just need to weigh up the pros and cons really.
Unless he's guaranteed to go straight into a salary well above the national average on graduation, the repayment of even a small portion of any student loan is likely to be sometime in the future. And the amount repayable each year depends on the amount he earns over the threshold, not how much he has borrowed.
In the meantime, your savings, once spent, are spent. If your DS needs financial support once he has graduated, there is no more that he can borrow, plus you no longer have the means to help him.