It depends on your level of earnings - if both of you earn over the standard rate cut off point of 33,800, there is no benefit to being jointly assessed. If one of your earns under this amount, you should be jointly assessed and split the tax credits / cut off point accordingly. In order to specify best division of tax credits / cut off point, you would need to post both of your annual earnings.
If your spouse is an employee of the limited company, he should be able to request a P21 online from PAYE anytime.