"basically if he doesn't sort it out I'll divorce him"
Wow - Just wow!
You have on of the most generous pension schemes available, which you are benefiting from, and good for you as its a very good scheme to reward our great health care system.
However, your contributions are no where near what you would need to pay in a DC scheme to receive the same level of remuneration. We are talking 25-35% of pay required. I appreciate that you are not asking for your partner to pay in this.
However, self employment is a tough gig. The way our tax is calculated can make payments on account huge, NI, non paying clients, delays in clients paying, fuel, materials etc - these all really hinder our ability to commit to a regular pension.
My pension, is the sale of my business, foolish? Maybe?
I do however pay into an S&S ISA, which allows me to take money out as and when my business or I may need it.
To divorce someone for not having a pension points to bigger problems if I am honest.