Actually, thinking about this, if you have one person per district, direct democracy, you need 50.1% to win a simple majority. If you have one district with 2 parties and FPTP, you need 50.1%. But overall, you need about half the votes per district and about half the districts for a simple majority, which means for most values of districts and people per district, you need about 25% of the vote. Near the extremes of number of districts and the number of people per district, you can see fluctuations up to just over 50% and a fair amount below 25%.
Actually, thinking about this, if you have one person per district, direct democracy, you need 50.1% to win a simple majority. If you have one district with 2 parties and FPTP, you need 50.1%. But overall, you need about half the votes per district and about half the districts for a simple majority, which means for most values of districts and people per district, you need about 25% of the vote. Near the extremes of number of districts and the number of people per district, you can see fluctuations up to just over 50% and a fair amount below 25%.