Wifi not reaching our office- alternative options to extend beyond Wifi Pods

Hi everyone, looking for some advice. 

We currently have a Volt M250 package with Virgin. The signal generally has been good within the home, the issue is that our Wifi does not extend to our office. We live in a middle terrace & we have an outbuilding at the back of the property which functions as an office. Since moving in, we've been unable to get Wifi there. our telephone connection (& therefore Wifi hub) is at the front of the property. 

I've contacted Virgin who have provided two Wifi Pods which we have placed as far back in the property as we can in the hopes that it would extend the Wifi to the office, with no success. I think the issue comes that the pods have to essentially extend the network through two brick walls? The reason I say this is that the distance between the Wifi pods/extenders & the office is no more than 10-15feet. 

Anyway, my question now is what are our options? I'm left wondering if there is a stronger extender that may be able to fix the issue, or if I will need to bite the bullet & look into fitting ethernet cables to extend more effectively.

Thanks