nighthawk m1 wireless v USB

Hi

Nighthawk kit arrived yesterday, easy set up etc.

4 from 5 bars reception shown...so that's fine.

if i connect to device by USB, again no issues, 20+mbps download (which compared to Sky broadband of 1mbps) is lightning fast for my location.

If I try wireless (even with kit sitting next to laptop) drops to 14mbps.

If I move NH to other end of the room, but still in clear line of sight, then drops to less than 2mbps.

TV Streaming not possible - even in the same room.

Suggestions please.  Getting desperate as NH and o2 are my last resort.

I have some extenders but not sure if these are compatible or if i need to do anything techincal with them