BA London not interested (with exception of being prepared to sell me full priced Business Class flights home).
Despite being stranded in Atlanta with wife and kids would not phone me back with any options to get back home.
Spoke to Exec Club who said I could not use companion vouchers and I didn't have enough miles to get back without them.
By companion vouchers, I assume you mean the Amex 241 vouchers rather than Gold Upgrade For Two vouchers. Assuming that's the case, then as Amex 241 can only be used for journeys ex-UK, the Exec Club were right in saying you can't use the companion vouchers.
Given that and as you didn't have enough miles in your account, what else could BA have done except say that you could buy new tickets ?
Z class ? I thought most economy tickets are changeable (after paying a fee and subject to availability) ?