Has anybody any idea how we can update the nameserver IPs with netsol?
The domain for the NS is not registered through them (obviously) and any efforts to contact their support staff have met with the usual "I'll send you this completely irrelevant reply, as I hate my job"
Yes that is true.
It does not matter what NetSol has in their whois information. That is just a pretty way of showing all of the information and it is often wrong.
All that matters is that your registrar has the correct information when you registered your name server (or changed your IP).
They should contact the regstry and update the A records for the root name servers for your domain extension. Because that is all that matters anyway. Since those are the records returned in the glue records (know where to look for your name servers).
Netsol has a bad habit of not always updating their WHOIS records. They have implemented a certain level of security measures for just checking the ownership of a domain. Their entire system needs a rewrite in my opinion. I hate working with NetSol, but I do have a couple of domains there and those clients don't want to transfer to another registrar.
As long as it shows up clear at one of these sites, as well as your registar, there should be no problem: www.dnsstuff.com
Most people that I know of don't even use NetSol to check WHOIS records on domains.