Does the shareholders agreement say how about valuation?
Comments like its a solid business and €200k turnover are a bit irrelevant.
What's the gross profit, what the level of directors remuneration, what's the net profit.
What the value of the assets in the company?
If you leave to the have to bring in someone else to do your job.
Needless to say what ever you think it's worth the other side will think it's about half.
You have a couple of options sell to the other shareholder, sell back to the company or sell to a third party. There is also a payment for compensation for loss of office which is tax free which works in some cases.
In most cases the third party option is not feasible and the other party can't afford to buy so you left with a company buy back.
In a lot of cases the company accountant represents all three parties and can broker a deal that suits. But if you want to go to another accountant first that's fine but there will be a trade off from what you want.