U.S. employees typically receive ISOs.
Non-U.S. employees / contractors typically receive NSOs.
Employees are free to exercise their vested options at any time, unless the company is actively engaged in a financing round. In which case, we encourage employees to wait until after the round closes and the new 409A valuation report (establishes the latest fair market value) is available to exercise their options.
Early exercise requests are evaluated on a case by case basis (depending on local regulations and expenses considerations, etc.). Please discuss with company legal counsel on appropriate steps.
Since UK employees are engaged through a PEO, company equity plans would not qualify for EMI (Enterprise Management Incentive).