I'm in exactly the same situation.
I have been employed for several years on a non-statutory type contract in a third level institution. As with you, my salary depends on the level of business that our research group can bring in and as such our security of employment is the same as that of any private sector employee - i.e. we're made redundant quite easily if we can't get sufficient funding to pay our costs. While we do get some of our funding from the government in the form of research contracts we have to tender & compete for this in the same way as we do for funding which we get from industry. As such, we are just like a business and our staff are not directly on the public payroll. Our salaries are also lower than the public service average and simialr to the private sector average.
For most of the time I have been in this job, we contributed to a defined contribution pension scheme which was run by the university in parallel with the DB scheme which was for statutory staff. However, last summer the university moved all of us into the DB scheme. This was very welcome as it does gives us a better pension but it does not seem entirely fair that we should have to pay to the same levy our our "statutory" public service colleagues given that we do not enjoy the protections they have and are not been paid directly from the public payroll in the first place.
The public service pension scheme is undoubtedly very good, but it has some drawbacks for people like us. You must really have a long period (i.e. 40 years) of continuous service to get the benefits. If you're in a situation where you only build up short periods of service (caused by redundancy), the benefits are not great. It's also impossible to transfer service from the public pension to a private one if you're lucky enough to find a job in the private sector.
I think we're a group that have been forgotten about in the planning of this levy. I'd be interested to know if anyone has any information on this as I haven't been able to find out anything yet.