Is it permissible to send dirty clothes from Hajj to be laundered at the company's expense, given the unavailability of a suitable place for washing in the accommodation, and can the company be compensated by manually washing a similar quantity of clothes later?

Believers are bound by their conditions, and the contract is the law between the contracting parties, so long as it does not violate a Sharia (definition) ruling. If your contract with the company does not include the cost of laundry during holidays, then it is not permissible to do so at the company's expense unless the company permits it. In the event that the company does not permit it, then the questioner's responsibility is occupied with the value of the benefit of washing these clothes, and this value must be returned to the company, or an equivalent amount deducted from his entitlements.