I have no qualifications, but I have been part of several EMI schemes.

Your option contract should state how you would go about excising the vested options. You may discover that there are additional secret agreements that the shareholders all have to agree to. However, you might want to get the person saying it's "too complicated" to explain it to you.

The options should have been granted at what was agrees with HMRC to be a fair value at the time of the grant.

If that's the case, then:

You will not have to pay Income Tax or National Insurance if you buy the shares for at least the market value they had when you were granted the option.

https://www.gov.uk/tax-employee-share-schemes/enterprise-management-incentives-emis

Also, CGT is only when you sell the resulting shares (assuming you ever can)

If you exercise your EMI option the capital gains cost of your shares is what you pay for them together with the amount charged to Income Tax, if any, on the exercise of your option.

From: https://www.gov.uk/government/publications/employee-share-and-security-schemes-and-capital-gains-tax-hs287-self-assessment-helpsheet/hs287-employee-share-and-security-schemes-and-capital-gains-tax-2019#enterprise-management-incentives-emis

However what you do have is an illiquid asset, which could cause problems, for example on death I don't know how inheritance tax would work - I assume it would be based on the nominal value at that time, even though the estate would be unable to sell the shares and so raise any money to pay the tax due.

I have no qualifications, but I have been part of several EMI schemes.

Your option contract should state how you would go about excising the vested options. You may discover that there are additional secret agreements that the shareholders all have to agree to. However, you might want to get the person saying it's "too complicated" to explain it to you.

The options should have been granted at what was agreed with HMRC to be a fair value at the time of the grant.

If that's the case, then:

You will not have to pay Income Tax or National Insurance if you buy the shares for at least the market value they had when you were granted the option.

https://www.gov.uk/tax-employee-share-schemes/enterprise-management-incentives-emis

Also, CGT is only when you sell the resulting shares (assuming you ever can)

If you exercise your EMI option the capital gains cost of your shares is what you pay for them together with the amount charged to Income Tax, if any, on the exercise of your option.

From: https://www.gov.uk/government/publications/employee-share-and-security-schemes-and-capital-gains-tax-hs287-self-assessment-helpsheet/hs287-employee-share-and-security-schemes-and-capital-gains-tax-2019#enterprise-management-incentives-emis

However what you do have is an illiquid asset, which could cause problems, for example on death I don't know how inheritance tax would work - I assume it would be based on the nominal value at that time, even though the estate would be unable to sell the shares and so raise any money to pay the tax due.