Well I guess if you are the company owner paying an employee, it is an expense. If you are the employee, its a taxable benefit. So maybe you pay £2k as an expense and pay 40% tax on £2k as an employee....im sure an accountant will be along soon to advise
It would probably be cheaper overall if your other half has company paid for PHI and can add you on whether she pays the additional BIK or the premium uplift.