HH5 on Infinity 1 has trouble reaching mac air while sitting in my garden, though it's not that far.
Originally my old router was positioned in the hall, pretty much direct line of sight to garden when kitchen door open.
Newly installed BTHH5 was positioned upstairs so that tv could connect to router via ethernet cable, engineer stated the faceplate in the hall was now 'redundant'.
Would Wi-Fi extenders the 1200 version be tha answer here?
No, I would not recommend any type of range extender, as they do tend to degrade the wireless speed.
It would be better to use one of these and position it in a room overlooking the garden.