We have been getting same problem. Suddenly our security camera wont connect and also my husbands phone when he takes it upstairs! I might add his phone is on contract from bt, weve had no problems before. Just suddenly started.
After a firmware update it is best to do a factory reset of the Homehub by pressing a pin into the recess button on the rear for about 20 seconds.
Pin factory reset makes no difference. Wireless download speed seldom reaches double figures and sometimes as low as 1 or 2 mbps. Wireless upload speed around 5 or 6 mbps.
Wired connections regularly achieve download speed of 35 mbps and upload speed of 7 or 8 mbps.
So big difference between wired and wireless download speeds and almost parity on upload speed.
Wireless speed tested with devices in same room as router. Android and Apple devices.