1 night per fortnight is not much - As your partenr lives too far away for mid week contact to be practical, I would have thought that Fri - Sun would be more reaspnable, plus generous holiday contact.
However, If the order was only made in April this year, I think your partner is going to struggle to get a change as the oder was only made 3 months ago (unless there has been a significant change in circumstances)
It is also inappropriate for your partner''s ex to be putting their child in the position of being expected to ask for more - he is FOUR, for heaven''s sake - he needs his parents to be parents and to make that decision for him.
It may be worth his while to write or email to her.
he shoudl set out politely what he proposes, explain that son enjoys the time with his dad, and asks about staying longer.
If the order provides for "such further and other contact as may be agreed" then flag this up, and remind her that it was envisoned when the order was agreed that thee two of them would be flexible and would agree additional contact (if that is true)
It may be worth suggesting that you have a trial run of just one weekend wioth a longer vist, with assurances from your partner that he will bring son back early if he seems at all unsettled.
Ask whether seh is willing to go to
mediation to discuss contact.
None of this may work, but if she responds and gives reasons for her views it gives him something to work with.
I think if he waits until the rder has been in place for at least 6 months he would have a better chance as he would be able to point to a longer period of her not being flexible or being willing to agree to additional contacts.
The other issue (which is always very hard) is to consider what impact more court proceedings and (invitably) increased stress/hostility will have on his son. I am sure his son would enjoy spending more time with dad, but even if he is sucessful it does come at a cost to his son .
n summery - I think moer contact would be reasonable - I suspect it may not be achieveable right now and unfortunatly the down side of applying will be there whether he suceeds or not, in terms of the added tress for his son (not to mention the stress and finacial cost to him personally)
Is it possible for your partner to visit his son closer to home in the week? it may be worth suggesting that s a short term compromise.