You can arrange to buy / sell* US stocks with a minimum order value of £1.

*Please consider that the minimum sell order value is £1 when partially transferring money out of an investment in a particular US company stock, to avoid ending up with a balance of ‘loose change’ that doesn’t fulfill this order criteria (in which case you can either wait for the value of the stock to potentially appreciate in value, or invest an additional amount to take the total balance of your investment in that stock to £1).