Don't even think about repeaters.
Go on ebay and find a new (BT) 2wire 2700 hub. They can be found new for £5-10.
Install an Rj45 socket near to the current hub and another in the area lacking coverage and link te two with Cat5e cable. Connect the existing hub and 2700 giving the 2700 a fixed IP and turn off its DHCP and there you have it. Done and installed for £20 or so.
M H C
taurus excreta cerebrum vincit