Mind out if you have a mortgage on the property. If you let it to the MOD via countrywide (unaware that they had changed their name! But as long as the rent keeps coming in!) you are effectively renting it to a commercial company and you need a business mortgage rather than a normal buy to let, I had real snags come re-mortgage time. If you have any snags IM me and I will point you in the right direction. You also need to inform the UPO you are renting it out if you have LSAP. They will charge you a letting fee ontop of your normal repayments.
Countrywide also only act in the capacity to rent the house out, so only charge about £20 a month. They will not deal with stuff that you would expect a normal agency to do, such as periodic house inspections, gas & central heating inspections, organising repairs if needed etc. If you are remote from the property, get a proper agency first and then get them to rent the house to countrywide.
Also, if the property is empty, you won't get paid. But countrywide only take on property they require, so as soon as they don't need it, it will be vacant and you will be back to square one.