You could get another booster and point it down the garden - but only if you qualify for a free one - if you are paying £3/mo you would be better advised in getting your own better quality wireless equipment.
Is it to a garden room of some sort that has electrical power to it? If its just sitting out at the bottom of the garden, then I would get an exterior grade wireless access point and mount it on an exterior wall pointing at the area. It would need a power supply and connecting to the Hub by ethernet cable though (can do both on one cable).
Another solution would be to ditch the booster and get your own wifi Mesh system and place one of the units as close to the location as you can (window ledge?).
-------------------- John --------------------
My services: HD TV on VIP (+ Sky Sports & Movies & BT sport), x3 V6 boxes (1 wired 2 WiFi,) SH2 in modem mode with Airport Extreme Router. On VIVID200, Talk Anytime Phone, x2 Mobile SIM only iPhones.
Yes its for a garden room so there is an electric supply there. If we have another booster we would have to pay the £3pm as far as I'm aware. So, theres something we can get to install there rather than having a virgin booster?